Light & Darkness

One of the first things you notice about the Underworld, once you get right down into the belly of the place, is that it’s dark down there. I don’t mean like a gloomy night with heavy clouds and no moon, or even a hide-in-a-cupboard kind of dark where you close the cabinet door, cover your head with a blanket, and listen to yourself breathe—not that I’ve ever done that, of course! But I’ve heard others talk about it.

No, the darkness of the Underworld is a pure dark. It is the default condition, so to speak, unless there is some unique feature creating visible light. And every experience, every waking moment, every facet of Underworld life begins with this key fact. It cannot and should not ever be forgotten.

Of course, there are some beasts that have completely adapted to existence in a lightless environment. They often compensate with exceptional development of their other senses—a keen sense of smell, or an otherworldly ability to hear. The bat is a perfect example of the latter, f lying blindly through often serpentine passages, yet using the reflected echo of its own squeak to avoid crashing headlong into a solid stone wall.

The lack of reliable light under the ground is the single most important feature of that environment. How a character, and a party, adapts to that lack will go a long way toward success, and likely even survival. So be prepared! 15 It would be worth reminding the reader that magical light has the advantages in that it doesn’t rely on oxygen, won’t ignite other invisible gases, won’t smoke and potentially obscure the vision it is meant to aid, is more reliable and consistent, isn’t going to set materials alight in the heat of battle, doesn’t need to be held, won’t go out if placed on the ground or knocked over, and is much less encumbering.

The next step of visual acuity on this sensory scale belongs to those dark-dwellers such as the dvergr and drow, and gnomes and us dwarves in general to a lesser extent. Other creatures too, fell beasts and unnatural aberrations, also have this ability.

However, while these types can’t discern details in shape or form with their eyes, they can detect the presence of varying heat with them. This allows them to locate living, warm-blooded creatures with considerable accuracy, giving an obvious advantage in combat and movement against sightless foes. It also allows observation of objects warmed by fire or hot water or other sources. But it doesn’t let them make out every detail of an underground cavern where everything is the same temperature.

To do that, to see all the details available to the dwarven—or human or elvish—eye, one must provide one’s own source of light. To this end, even more than the need for food and water, the ability to create and use light under the ground is one of the keys to not just survival, but to flourishing.

Unfortunately, at the same time, light presents a significant danger to the light-wielder because it is an obvious announcement of one’s presence and location; that is, creatures of the dark can become aware of you, and even move in on you with dangerous intent. If they’re quiet they can get pretty close before you even have a clue that they’re anywhere nearby! So light should only be used in a very safe environment, such as a lair or a fortified camp, or when it is absolutely necessary to the delver’s mission.

Obviously, the most common and readily available source of light involves setting fire to some kind of burnable fuel—a torch, the wick of an oil-fueled lamp, and so forth. Though I’m no fan of magic, I have to admit that certain spells, as well as numerous magical devices, have the ability to cast enough light so that the magic user and her companions can at least get a look around. So, there’s that.15

But remember, there’s no fluorescent fungus waiting for you on every corner, or helpful glowing spores floating wherever you wander. I’ll say it again; the Underworld is darker than the belly of a shadow dragon, and I should know! But that’s a different tale worthy of another round of this mushroom stout, my friends, so let’s see you make haste to the barkeep…

Light

The sudden appearance of ANY form of light should be a warning. It is always worth remembering that light advertises the party’s presence to every other creature in the Underworld.

1. Torchlight may mean: someone is there with a torch; a torch has been left behind, perhaps as a trap or because the owner was eaten by something that didn’t want it, or they’ve been dragged off by a race that doesn’t need light; it might be magical and everlasting, although why a valuable treasure would just be abandoned is unclear

2. Luminous fungus might mean: a feeding ground; or the guarded entrance to a lair; or a trap or lure; or an area where molds, slimes and fungi are just deadly in their own right

3. Sparkling can mean: a change in type of rock, which might indicate a mine and therefore another race’s territory; or a lair decorated with trophies or beautiful items; or a disputed place where money might be made supporting one side or the other

4. Is there a biomineralized or biocrystallized creature lurking in a stalagmite-strewn cave reflecting even the smallest amount of light away from itself; or some outlandish mold that is carrying gold-riddled bacteria within its surface?

5. If the light is from heat, is it fire or lava that is rapidly using up oxygen and producing other gases, or possibly a site of a portal where elemental creatures appear? Might the glow come from a gate of some sort?

6. Is there a drow party attacking some poor benighted being now outlined by a magical incandescence?

7. Is the gleam coming through cracks in the rock that suggest there is a fire-using encampment “just the other side” of a five-foot-thick wall and its users don’t know you are so close to them.

8. Although usually associated with the darkest necromancy, there might be a glowing undead creature ahead, whether a Large ghost or Tiny will-o’-wisp.

9. Is the light subtle, perhaps from a magical weapon? Is the glow a sign to warn the owner of a nearby foe, or is the bearer tracking a creature that is, in turn, following the party?

10. Is civilization, or at least a community, just around the corner, and the illumination comes from its first homestead or guard post?

The core rules recognize a variety of different ways of perceiving the world:

• Sight. The most common means of perceiving the world.
• Blindsight represents means to see creatures without relying on sight, such as echolocation. It typically ranges from 10 feet to 60 feet. (For a more simulation-based take on how to represent sonar-based sight, consult the vestraadi race in Underworld Races & Classes)
• Darkvision usually has a range of 60 feet and lets you see in dim light as if it’s bright light, and in darkness as though it was dim light. Beyond its range, things blur into a fog, and Darkvision is only in shades of gray. Darkvision otherwise depicts the world as regular sight does. Superior Darkvision has a range of 120 feet instead, and often is accompanied by Light Blindness, Sunlight Sensitivity or a similar drawback.
• Tremorsense lets creatures detect and pinpoint vibrations in a specific radius but cannot perceive flying or incorporeal creatures. Many burrowing creatures have this sense.
• Truesight pierces invisibility, darkness, the true forms of shapechangers, into the Ethereal Plane, etc.—it is basically the “I Win”-button of sight.

Other editions of popular fantasy games sport a variety of additional types of sight that you may want to consider incorporating in your game. You can use the following rules:

• Low-light Vision is a type of vision usually found among surface elves, fey and similar beings. You can use it to replace Darkvision for such creatures. Low-light vision lets you see twice as far in dim light—basically the distance of light shed by dim light is doubled for you.
• All-around Vision is a type of sight usually reserved to creatures with plenty of eyestalks. They can see in all directions at once, making ambushing them particularly challenging. Typically, this negates, e.g., advantage on attack rolls due to attacking a creature’s back. If a creature has a lot of flexible eyes, consider granting this type of sight.
• Infravision was the most common type of sight for dungeon – dwellers and creatures from the realms below before being replaced by Darkvision. If you’ve ever wondered about drow being able to see heat, as famously depicted in earlier installments of a series of books about a certain renegade drow escaping his cruel home, Infravision is the reason for that.

Infravision, unlike Darkvision, did not always have a maximum range, sometimes extending as far as the eye could see, and it did not depict the world in black and white—instead, it was basically heat vision, showing hot spots in red, cold ones in blue, and so on.

Infravision warrants special attention, in that it offers a whole array of options that Darkvision does not. As a heat-based sight, switching to Infravision could radically alter how environments looked—a drab cavern might be covered in rainbows of light, huge stalactites might measure time in descending rings of heat. Undead and some constructs might be all but invisible to Infravision, whereas some creatures, like massive fire elementals, may be literally blindingly bright. While Infravision lets you see heat, it does not necessarily help you discern between details of cold equipment—seeing a cold metal ring on a cold metal floor will be harder…this adds a whole array of tactical and roleplaying options to the game. The party might track a warlock sniping them with fire through the glowing lines, see raised temperatures of those affected by epidemics, or realize at a glance that the corpses they just found haven’t cooled—there are many options, and it is hoped that you consider reintroducing this beloved classic in your game.

Introducing Infravision

You can introduce Infravision with a few straightforward considerations. Start by simply telling your players you intend to incorporate it and then think about:

• Whether a creature sees in the dark courtesy of magic or not—if they can see due to magic, Darkvision makes sense.
• If the species or race in question is often exposed to fire (such as dweorg working their forges) or are creatures native to a biome with lakes of fire etc., Darkvision also makes sense.
• If the creature has Light Blindness, Sunlight Sensitivity or generally lives in a biome without light, or with very few sources of light, Infravision makes sense.
• If you replace Darkvision with Infravision, as a rule of thumb, Infravision should have 1.5 times to twice the range of Darkvision.
• If you replace Superior Darkvision with Infravision, then as a rule of thumb Infravision should have no maximum range.
• Alternatively, you could just make Infravision an alternate mode of seeing that all or most creatures with Darkvision have.
• The darkvision spell should alternatively be able to grant Infravision instead.
• Magical darkness should thwart Infravision if it would thwart Darkvision.

Few things define the Underworld as much as the absence of sunlight, so let us summarize the common sources of light available to the average adventuring group.

• Candles shed light in a 5-foot radius, and dim light for an additional 5 feet. A candle lasts an hour.
• Torches provide bright light in a 20-foot radius, dim light for another 20 feet. A torch burns 1 hour.
• Lamps cast bright light in a 15-foot radius, dim light for another 30 feet. A flask of oil makes it burn for 6 hours.
• Bullseye lanterns cast bright light in a 60-foot cone, dim light for another 60 feet. A flask of oil makes it burn for 6 hours.
• Hooded lanterns cast bright light in a 30-feet radius, and dim light for another 30 feet. A flask of oil makes it burn for 6 hours, and the hood may be lowered as an action, reducing the light to a 5-foot radius of dim light.

There also are some common spells that generate light as a byproduct:

• The faerie fire spell makes the objects and creatures affected shed dim light in a 10-foot radius. It can only be concentrated on for up to 1 minute.
• The flame blade spell sheds bright light in a 10-foot radius, and dim light for an additional 10 feet. It can only be concentrated on for up to 10 minutes.
• The flaming sphere spell sheds bright light in a 20-foot radius, and dim light for another 20 feet. It can only be concentrated on for up to 1 minute.
• The holy aura spell sheds bright light in a 30-foot radius, and creatures in the spell’s area upon it being cast may, at the caster’s choice, shed dim light in a 5-foot radius. Note that this light represents a definite boundary—the aura does not shed dim light beyond its original radius. It can only be concentrated on for up to 1 minute.
• The moonbeam spell creates a 5-foot radius, 40-foot-high cylinder of dim light. It can only be concentrated on for up to 1 minute.
• The sunbeam spell makes your hand shine a bright light in a 30-foot radius, dim light for another 30 feet. It can only be concentrated on for up to 1 minute.

In addition, there are some common spells that do not generate light as a byproduct, but as their primary benefit:

• The dancing lights spell creates 4 motes of light that shed dim light in a 10-foot radius. It can only be concentrated on for up to a minute, but its advantage is that it is a cantrip. Guards and wards can make them last longer, but only in a fixed area.
• The produce flame spell creates fire that sheds bright light for a 10-foot radius, and dim light for an additional 10 feet. It can only be concentrated on for up to 10 minutes.
• The light spell sheds light in a 20-foot radius, and dim light for an additional 20 feet. It lasts an hour.
• The daylight light spell creates a 60-foot radius sphere of bright light, dim light for another 60 feet. It lasts an hour.

As can be gleaned from the above, lamp oil burns longest (6 hours) which is still less time than a long rest. For the purpose of facility, tracking fuel via the units of stock system presented in this site is suggested for monitoring light conditions while resting. A small campfire is assumed to shed light akin to a hooded lantern, though larger campfires can be created at the cost of more units of stock.

The relatively short duration of most lighting options offers a unique challenge for those planning to venture forth into the Underworld for prolonged periods of time. As such, a variety of light sources are presented below. The Underworld light sources cannot be bought typically, only found or bartered for.

Underworld Light Sources

The following light sources are known to have been used in the darkness below. Some will be available for normal prices, some will be impossible to purchase, and others will only be found or bargained for with unimaginable currencies. As anywhere else in the realms below, scarcity and environment determine availability—in the Lightless Abyss, for example, any source of light might be worth its weight in gold.

As GM, be creative with other potential light sources. The Underworld is known for the exotic if nothing else.

Antibee Candle Lamp

Black, bee-shaped holes gather anti-pollen from the absence of flora, killing any plant matter they accidentally come into contact with. In hives tended by eccentric drow apiarists, black honeycombed wax congeals from this “nothing”. Antibee candles generate no light when lit, unless viewed through Infravision: the region lit by antibee candle lamps shows as regular sight would see it in proper light—i.e. full color. Beyond the range of the anitbee candle (depending on the lamp, see Table 9-1), Infravision again shows the world in its usual diffuse, thermal rainbow.

Beetle-Stick

A favorite of primitive cultures, this is a stick with a small platform atop. On the platform, a fat, cat-sized beetle sits, its legs tied to the stick with fine moss ropes. The beetle emits a constant, bright light in a 10-foot radius, and dim light for another 10 feet, with all colors available for purchase in the markets below. The beetle can only generate light for 8 hours per day.

As an action, the docile beetle may be agitated, flying around and shedding twice as much light as usual for 1d10 rounds. An agitated beetle has a 10% chance of dying from attempting to escape. The beetle must be fed at least one unit of stock every 13 days, or it dies.

Blood-Ant Lamp

Eyeless, angry crimson-red ants with jagged, sharp chitin are held within a crystal globe. The ants feed on blood and are ostensibly creatures of Hel—they emerge and return to their lamp on command. If fed at least the equivalent of a Tiny creature’s blood, the ants glow with a bright, angry red light in a 60-foot radius, and dim light for another 60 feet, for 1d3 days. A character can burn a Hit Die to feed a blood-ant lamp.

Blood-ant lamps are rare and only ever bestowed to someone, never bought. A common way to attain them is via infernal bargaining and ritual—the gitwerc in particular are fond of these insects. If an owner sells the lamp, the ants fail to work for the purchaser and seek to escape as soon as possible. Once free, they hunt down the former owner to exact deadly revenge, after which they return to the person who had previously best cared for them, which may of course be the character who bought the lamp.

Carbide Lamp

These lamps burn with a comforting, bright, white light in a 45-foot radius of bright light, and 45 feet dim light beyond, negating some of the horrors below. These lamps grant +1 resting penalty modifier.

They also produce and constantly leak toxic sludge that slowly destroys local ecosystems. In regions that have been exposed to copious amounts of carbide sludge, foraging and hunting checks are made at disadvantage. To represent the effects of concentrated carbide sludge in combat, use the Underworld Hazard generator.

Carbide Lamp, Svirfneblin

Refined by the svirfneblin, these lamps emit an even brighter light, granting a +2 resting penalty modifier in a wider radius. However, they also generate more sludge and can only be maintained by a svirfneblin transgnomamist (Occult Secrets of the Underworld, page 49) or a similarly svirftech-versed individual.

Cephalo-Lamp

Atop a stick, a crystal bowl houses a crammed, semi-translucent squid that pulses with constant, soothing patterns, like a living lava lamp. The squid emits bright light in a 60-foot radius, dim light for another 60 feet. The calming ripples grant a +1 resting penalty modifier. The squid’s water must be changed every 7 days, consuming a unit of stock. Additionally, the squid must be fed every second day, consuming another unit of stock.

The squid is intelligent and does not take kindly to being improperly cared for. It has its own agenda that may or may not overlap with the party’s goals, but it can be persuaded to help with aquatic-based aims if given water and food more often.

Deepwhale Oil lamp

The oil of the deepwhales, colossi that inhabit pitch-dark subterranean seas, burns slightly brighter than regular lamp oil (+25% of standard oil distance), but its scent and soot are infused with a profound, existential sadness. Sleeping after being exposed to the light of this lamp makes waking up less reliable—add +1d3 hours to the hours the individual sleeps, dreaming of loss. Enslaved Spirit. These lamps are rare, containing a spirit of fire or similar magical being, enslaved and trapped within. The creatures rage constantly, and previous allies of the being attack the owner on sight. These lamps are never sold for money, but always bartered for, their worth being an indicator of the new owner’s power.

Flicker-fishes

This bowl of fluorescent, eyeless, piranha-like fish glowing sickly purple casts bright light in a 40-foot radius, and dim light for a further 40 feet, up to 1d6+4 hours per day. The fish can be shaken in a specific way as an action, prompting them to autocannibalize, which generates a strobe-like effect for 3d6 rounds.

While strobing, creatures using Darkvision or Infravision in the flicker-fishes’ light are blinded on a failed Constitution saving throw against a moderate environmental hazard DC (Underworld Hazards). After strobing, only one fat fish remains, glowing happily. To strobe again, new fish have to be inserted. The fish must be fed a unit of stock every 3 days or they will randomly begin to autocannibalize, and strobe, at an unfortunate moment.

Greenfly Lamp

Turquoise-greenish firefly-sized insects buzz inside a copper lamp and emit bright light in a 10-foot radius, and dim light for another 10 feet. The insects live for 7 days before dying. Adding chlorine gas quadruples the radius, but kills the insects after 1d10 hours.

Helfire Lamp

Only carried by the gitwerc and their infernal masters, or the few that bested them, these lamps contain a demonic spirit or lost souls, burning eternally with the fires of Hel. They shed reddish-black light in a huge 90-foot radius, and dim light for another 90 feet. In this radius, Darkvision is red-black instead of shades of gray. Very clearly evil, there is always a price for these lamps, but one that few are willing to pay. The spirits within often vanish or fail when least convenient for the party.

Mushroom-Stick

A fluorescent mushroom on a stick that sheds bright light in a 15-foot radius, and dim light for another 15 feet. It only glows for 2d6 hours after being harvested.

Portable Portal Lamp

Either invented by a mad svirfneblin, a crazed mage, or someone who was both, these lamps are semi-stable fist-sized portals to another plane. While they may shed bright light in a 90-foot radius, and dim light for another 90 feet, there is a cumulative 1% chance each day that something comes through the portal or attempts to rip it open further. Proximity to the Amber Roads may also trigger a tear in the planar fabric.

Woundfire

The only source of light that can be found reliably within the Lightless Abyss biome, woundfire is a type of bacteria that grows on the flesh of flensed body parts or open skin, emitting cold, cobalt-blue flames as it burns using wounds and damaged flesh as fuel. Woundfire sheds bright light in a 10-foot-radius, and dim light for another 10 feet.

A creature that has woundfire applied to an open wound begins emitting light, affecting the target as though a non-magical faerie fire until the wound is healed or properly washed, consuming a unit of stock. Dwellers of the Lightless Abyss often wrap decayed, woundfire-infected flesh around sticks to use as grotesque, nauseating lanterns.

In real life, the strength of a light source is measured in Candela, made up by luminous power per unit solid angle emitted by a point light source in a particular direction, with 1 candela equaling approximately the same illumination as a candle.

In game, one candela would thus provide a 5-foot radius or bright light, and a 5-foot radius of dim light. Since using candela as a unit of measurement requires some calculation, this site proposes a new unit—the Light Unit, or LU.

One Light Unit is the equivalent of light required to provide a 1-foot radius illumination of bright light, and again as much dim light. If a second value per entry is provided, this secondary value denotes the range of dim light. Such a value is only provided if the dim light emitted has a different area than the area of bright light. A “C” indicates that a source of light emits cold light that cannot be seen with Infravision.

Table 9-1: Different Light Sources

Light Source	LU	Candela	Duration Per Unit
Upperworlder Light Sources
Candle	5	1	1 hour
Torch	20	4	1 hour
Lamp	15	3	6 hours
Bullseye Lantern	60	12	6 hours
Hooded Lantern	30	6	6 hours
Common Spells
dancing lights	0/10 (x4) C	0/2 C	Concentration, up to 1 minute
daylight	60	12	1 hour
faerie fire	0/10 C	0/2 C	Concentration, up to 1 minute
flame blade	10	2	Concentration, up to 10 minutes
flaming sphere	20	4	Concentration, up to 1 minute
holy aura	30/5	6/1	Concentration, up to 1 minute
light	20	4	1 hour
moonbeam	0/5 C	0/1 C	Concentration, up to 1 minute
produce flame	10	2	Concentration, up to 1 minute
sunbeam	30	6	Concentration, up to 1 minute
Underworld Light Sources
Antibee Candle Lamp	15 C	3 C	1 hour
Antibee Candle Bullseye Lantern	60 C	12 C	1 hour
Hooded Antibee Candle Lantern	30 C	6 C	1 hour
Beetle Stick	10	2	8 hours
Blood-Ant Lamp	60	12	1d3 days
Carbide Lamp	45	9	8 hours
Carbide Lamp, Svirfneblin	60	12	8 hours
Cephalo-Lamp	60	12	Indefinite while properly cared for
Deepwhale Oil Lamp	20	4	3 days
Enslaved Spirit	60	12	Indefinite
Flicker-Fishes	40 C	8 C	1d6+4 hours
Greenfly Lamp	10 (or 40)	2 (or 8)	7 days (or 1d10 hours)
Helfire Lamp	90	18	Indefinite
Mushroom Stick	10/20 C	2/4 C	2d6 hours
Portable Portal Lamp	90	18	Until collapse
Woundfire	10/20 C	2/4 C	Until healed

Darkness

The GM faces a series of special challenges when dealing with the description of darkness, one that will become rather obvious when running a prolonged campaign in the Underworld. How does one keep things fresh, and differentiate between different types of caves, chasms, and ebon depths?

GMing the Endless Black

The endless black, the stygian gloom, encompasses everything—conceivable it can hold, and thus conceal, anything. In short, it has a narrative potential that is absolute!

The image created by the GM is ultimately the camera that guides the potential interpretation of the Underworld in the mind’s eye of each player—and much like a camera, you can focus on a range of factors to create various types of impression. You have probably seen this before with combat, when a character runs into a room and a player only notices the big features, not the minuscule details, because they take different things from the description.

If you consciously use your ability to focus information, and then concentrate on the way in which you relay that information, you have a whole new array of potent tools in your arsenal. Similarly, the sequence in which you present the information, and the quality and quantity of this information, all matter.

The world below can be comforting, threatening, majestic, and horrible, and what you describe, how you describe it, and the sequence in which you describe it, makes a difference. What you do and do not relate matters—some areas might highlight details, and some the overall complex. Some might make everything indistinct; some might be exact, with stark lines. Mentioning moods instead of describing details will generate a different impression. In a way, think of how different types of weather or light can affect you—and then apply this to caves and the endless black.

Picture a beautiful lightning storm, seen from the comforts of a cozy home. You experience a sense of awe and beauty; everything seems to be grander. Stark lines are drawn by lightning, underscored by thunder, while rain smooths the harsh outlines. We distill from that a sense of wonder, of awe, but not necessarily threat, unless forced inside unprepared. We experience a softness that hides and unifies details, punctuated by intensely highlighted, precisely-formed main features—bearing this in mind, we could translate the emotions and atmosphere to the game, to a new and wondrous environment. It is not only the weather that can act as inspiration. Think of an office comprising dozens of empty cubicles. The harsh artificial lights after all co-workers have left for the day. Only diffuse sounds can be heard. You are alone. Neon light and sickly-glowing screens hurt your tired eyes, creating supernaturally sharp lines dividing equipment from tables—and through the windows, there is the desolate black that promises no restful sleep.

From this, we fine-tune the sharp contrasts and accents; details over the grand picture. A confusion of specifics that makes the general picture hard to grasp—indeed, it is diffuse, something presses in from the outside, implying a threat of implosion, or of imminently collapsing in.

Think of how environments make you feel. Distill that essence. And then apply it to the boundless dark. The endless black can be everything, incorporate everything, and threaten everything. It can be a cradling mother, hiding you from your foes, at the same time as being the all-encompassing, uncaring void between the stars, come down to engulf you, cold and inhuman and vast. It can be everything you want it to be if you just describe it in the right way.

The endless black can be entirely different to a place of sudden, dramatic contrasts and inspiring changes. It is where the darkness itself gains weight and character, exhibits menace and a complete lack of concern for whatever exists in it. In short, the endless black becomes Darkness, which the under-prepared learn quickly to dread and shun.

Darkness

On Earth, the vast majority of living organisms exist in “dark biospheres”, places where light has never reached and may never do so. Of course, these organisms are generally small and insect-like, or are bacteria and viruses. But a fantasy realm such as the Underworld will produce many races and species that combine the lifestyle of our dark biosphere morphons with the day-to-day rhythmic controls demonstrated by, for example, almost all mammals. Many sages and those who are familiar with the deepest Underworld realms have long understood that their lightless caverns and passages are never empty—despite what others may think or say—because they are home to Darkness. At great depths, where sunlight cannot reach, and never has in many places, Darkness has become almost a living entity. The Darkness may be a sluggish, choking, cold, silent thing, but it is feared greatly as it bends everything it comes into contact with to its will over the limitless time it has at its disposal.

As such, at the boundary of the Lightless Abyss, creatures begin to change, warping in ways that can range from insidious to horrid. For example, a humanoid’s circadian clock, which is a rhythmic 24 hours long due to the cycle of the sun, begins to revert to around 24 hours and 15 minutes in low light, and slowly moves towards 24-and-a-half-to-25 hours as light is further reduced and extended periods without any illumination are introduced. A human will naturally begin to slow, mentally and physically, swapping a circadian, diurnal way of living for one that is initially more crepuscular, before adopting a nocturnal approach to activity and an infrandian rhythm, i.e. a cycle with a period of significantly longer than 24 hours and that completes less frequently than a circadian cycle. But why should this be? What is Darkness doing to creatures as they travel further into its murky depths? It becomes similar to swimming below the surface of a pool of ink, where very quickly all light disappears.

Explorers to the Underworld environs furthest from the surface are few, while visitors from those hidden domains are just about non-existent. Those legendary spelunkers who have made the journey to the edge of the Lightless Abyss and beyond and miraculously returned to their homes all talk about the same thing: the deeper they went, the slower, the weightier the light became. They describe how it doesn’t travel as far, or how the magical energy involved to get a spell to work properly becomes greater, or how it seems to take much longer than it should for this energized-yet-slowed light to bounce back to their eyes, sometimes so slowly that it seems as if whatever they were looking at was gradually materializing out of the air rather than being permanently in place just waiting to be seen.

Perhaps most worryingly, the extremely rare clerics who have quested downwards recount how they began to lose contact with their deity, and how the messages they did receive, whether spell revitalization or every day liturgical musings, were shrouded in opacity and required great concentration to understand fully. It is as if the gloom is actively attempting to cut off those that enter it from all they know.

Indeed, the further an adventurer travels in the Lightless Abyss, the less energy there is for light to function properly. Photons sparkle less, losing vibrancy; they begin to cool in the thickening shadow; as this happens, they slow, but their retained energy has to be dealt with; to compensate for the slower speed, the mass of the photons increases; and this of course in turn slows the photons further, as they aren’t able to draw on any more energy to maintain their speed.

Once light crosses the deep frontier of the Lightless Abyss, the near-living Darkness begins corrupting it. Initially, the changes are not obvious, because delvers are used to the effects of shadow magic, the Plane of Shadow, and similar outcomes. In fact, at first the particles retain a familiar behavior and appear to be little more than floating shadow, if they are seen at all. But this soon changes. Going deeper, the particles become weightier, and eventually take on characteristics that are in line with much heavier matter. This dark matter starts to manifest as a thin film that coats everything it touches, its presence detected only by the lack of sheen.

Sages also conjecture that light of every wavelength is affected by Darkness, and at present there are no reasons to believe this is not true. This means Darkvision and Infravision may be adversely affected, and that even Truesight may be challenged and less effective in certain circumstances

Plunging further makes eyes susceptible to entry by the Darkness and its dire will, a sentient infection that works against the vulnerable mind, twisting it, taking it, enslaving it. Eventually, those controlled creatures become part of Darkness itself, changing mentally and physically into unrecognizable versions of themselves.

Once a creature has acclimatized to Darkness, its appearance and vision are altered. Physically, its skin takes on an ultra-blackness that traps light (in order to add to Darkness) and provides the ultimate camouflage in this zone, one that turns them almost invisible when at great distances from the entry margins of the Lightless Abyss, and into little more than silhouettes in the best of conditions. Their skin cells become very fine but densely packed so that any light that hits them and doesn’t get absorbed isn’t reflected but instead is diffused back into the layer, effectively trapping the photons, slowing them, and converting them into Darkness.

At the same time, vision responds more slowly. An eye’s cones are used much less, robbed of the necessary brightness. Instead, the rods, capable of reacting to a single photon, increasingly gain importance, eventually growing out on stiff stalks that function as rods along their entirety, changing how the eyes look, up to the point where they can even become pedicels…

or strange jet-like pits in color and substance. Finally, as Darkness influences the host creature and converts it into a part of the whole, mental processes adapt along with their physical elements. The chemicals required to see light effectively become useless, so the chemistry of the brain changes allowing it to better respond to slow-moving, colder, less frequent “dark photons,” “dark matter” and Darkness itself.

It is possible to reverse these changes, but it takes magic of the greatest power and a slow journey back to the surface. For each day spent in the Lightless Abyss, it takes at least ten to reach the surface in much the same way as avoiding “the bends” when leaving the depths of the ocean.

Until a creature becomes one with Darkness (i.e. it exists for an appropriate period of time in the dark and does nothing to alleviate the effects of Darkness), it may suffer a range of effects when it continues to introduce light of any type into its daily routine. Table 9-2 below suggest a timescale for immersion into Darkness and possible effects if resistance is maintained.

Exactly how the following effects affect characters is left to the GM’s discretion. They are intended to be more strongly associated with a story-telling element rather than strict game mechanics in order to reflect the challenge Darkness presents on a day-by-day basis.

Table 9-2: Timetable for Becoming One with Darkness

Time	% Immersed	Effect of Immersion	Time to Revert
6 months	5	The creature can only see half the usual distance when they are in light, but twice as far when they are in dim light.	5 years
1 year	10	Sunlight hurts; an oily film covers the creature’s body. The creature has disadvantage on attack rolls, as well as on Wisdom (Perception) checks that rely on sight while in sunlight or particularly well-illuminated areas of bright light.	10 years
2 years	20	Standard light hurts; the creature has disadvantage on attack rolls, as well as on Wisdom (Perception) checks that rely on sight while in any light brighter than dim light. The creature appears shadowy.	25 years
4 years	40	Dim light hurts; the creature has disadvantage on attack rolls, as well as on Wisdom (Perception) checks that rely on sight while in any light. The creature gains advantage on Dexterity (Stealth) checks made while in complete darkness.	60 years
8 years	70	Skin absorbs all but the brightest light and turns either pitch-black or chalk-white; exposure to bright light deals at least 3 (1d6) radiant damage per round. The creature becomes invisible, even to Darkvision and Infravision, while standing still in the dark.	140 years
16 years	100	Invisible to creatures not suffering from the effects of this table. Contact with non-Darkness deities is lost.	320 years

Breathless in the Underworld

The standard rules for holding your breath state that a creature can hold its breath for a number of minutes equal to 1 + its Constitution modifier, minimum 30 seconds. When a creature runs out of breath, it can survive for an additional number of rounds equal to its Constitution modifier, minimum 1, before it immediately drops to 0 hit points and starts dying.

This differs from the real-world experiences most of us have had. In a calm situation almost every person can hold their breath for a minute or so, but when in strenuous circumstances, such as swimming against a current in choppy water, picking something off a pool floor, or even being weighed down when swimming fully clothed, the length of time you can hold your breath tends to decrease drastically.

The same holds true if you are caught unaware; it makes a difference if you consciously take a deep breath or are swept beneath the surface.

This means that while the rules are helpful and simple for the context of most regular adventuring, they provide only a relatively trivial framework to work with when tackling sinking rooms, lairs beneath the surfaces of lakes, staying alive after walking the plank, teleport traps into sealed barrels, and the like. Even the previously mentioned surprises aren’t accounted for by this basic system, leading to a potentially unsatisfactory in-game experience.

Therefore, if your group wants an added sense of realism, or requires a more dynamic engine to use when a party explores a partially submerged dungeon, chases off merfolk guerrillas, or struggles to escape a flooded pit beneath a locked trapdoor, we propose the following straightforward system for holding your breath.

Basics

Instead of tracking minutes, we will track Breaths. Each Breath is enough air to last a creature for six seconds, i.e. one round. Each creature holding their breath gets a minimum of 5 Breaths, which means they can hold it for 30 seconds, the equivalent of 5 rounds. Each creature gets this minimum amount of Breaths, regardless of the circumstances. However, a creature can also make a conscious decision to prepare for holding their breath, by Breathing in Deeply. This action includes using proper breathing techniques in a controlled manner.

Breathing in Deeply is an action that nets the creature 5 additional Breaths. A creature can only Breathe in Deeply if it can actually breathe in an unrestricted manner. Regardless of the creature’s Constitution modifier, it can Breathe in Deeply at least once, resulting in a minimum total of 10 Breaths if it prepares accordingly. If a creature is surprised, it is unable to Breathe in Deeply as an action during that round and therefore cannot gain the benefits of the action. However, any creature, even one that is caught unaware, gets an additional Breath per point of Constitution modifier, up to a maximum of 4 additional Breaths for creatures with a Constitution of 18 or more. Higher Constitution scores, or temporary increases to the creature’s Constitution modifier, are not taken into account for determining additional Breaths gained.

Adventurers and Holding Breath

A creature can Breathe in Deeply on consecutive rounds for increased benefits if meeting certain criteria outlined below. Each use of Breathe in Deeply nets 5 additional Breaths up to the maximum number of breaths outlined on Table 10-1. If a creature has a positive Constitution modifier, its fitness and robust physique allow it to retain more Breaths. A creature can hold a total number of Breaths this way equal to the minimum of 10 (the 5 Breaths minimum, plus the 5 for Breathing in Deeply) +5 Breaths per Constitution modifier gained through additional uses of Breathing in Deeply. As previously stated, neither a Constitution modifier of more than +4 nor temporary increases to Constitution are taken into account to determine the maximum amount of Breaths it can hold.

Swimming requires that air-breathing individuals have at least some experience with controlling breathing, making them particularly effective when Breathing in Deeply. This is also beneficial when holding one’s breath to stave off the effects of gas and the like.

If a creature is proficient in Strength (Athletics) checks—or just in Strength (Athletics) checks made to swim in rare cases—it can use Breathing in Deeply to hold an additional number of Breaths. The maximum additional times a creature can gain Breaths this way is equal to 5 multiplied by half their proficiency bonus, rounded down.

If the creature gains its proficiency bonus twice to Strength (Athletics) checks (or specifically-stated checks made to swim), it can instead hold an additional number of Breaths equal to 5 multiplied by their proficiency bonus.

If a creature has a natural swimming speed, but cannot otherwise breathe water, treat this as getting double proficiency bonus on Strength (Athletics) checks. Swimming speed granted by magic does not include the experience and techniques required to grant additional Breaths.

If a creature has a swimming speed and gains its proficiency bonus or double its proficiency bonus to Strength (Athletics) checks, the effects stack.

If a creature is surprised, it does not gain any benefit from its proficiency bonus or ability to swim as it cannot Breathe in Deeply.

The additional Breaths for a high Constitution and for being proficient in swimming stack with one another. Table 10-2 presents all this information graphically.

Table 10-1: Breaths and Constitution

Creature’s Base Constitution	Constitution Modifier	Maximum Uses of Breathing in Deeply	Maximum Breaths via Breathing in Deeply1	Maximum Breaths if Surprised
1	-5	1	10	5
2-3	-4	1	10	5
4-5	-3	1	10	5
6-7	-2	1	10	5
8-9	-1	1	10	5
10-11	+0	1	10	5
12-13	+1	2	15	6
14-15	+2	3	20	7
16-17	+3	4	25	8
18-19	+4	5	30	9
20-21	+5	5	30	9
22+	+6 upward	5	30	9

1 Total Breaths gained as follows: Base 5 plus 5 for one use of Breathing in Deeply plus 5 more per Constitution modifier (up to a maximum of +4) for each additional use of Breathing in Deeply.

Table 10-2: Additional Maximum Breaths Due to Proficiency or Ability

Proficiency Bonus	Creature’s Additional Maximum Breaths
	Proficiency bonus to Strength (Athletics)	Double proficiency bonus to Strength (Athletics)	Natural swim speed, can’t breathe water	Proficiency bonus and natural swim speed	Double proficiency bonus and natural swim speed
+2	+5	+10	+10	+15	+20
+3	+5	+15	+15	+20	+30
+4	+10	+20	+20	+30	+40
+5	+10	+25	+25	+35	+50
+6	+15	+30	+30	+45	+60
+7	+15	+35	+35	+50	+70
+8	+20	+40	+40	+60	+80
+9	+20	+45	+45	+65	+90

Sizes Beyond Medium and Breath

Larger creatures have a larger breathing apparatus, and as such, it makes sense that they can hold their breath longer. For the purpose of this system, we differentiate between magically-increased sizes, and natural sizes.

• Magical If a creature is of a size larger than Medium due to the effects of non-permanent magic, such as the enlarge/reduce spell, they calculate their number of Breaths as normal, but add +5 to the result for every Size larger than Medium. These additional Breaths are consumed first. If the magic effect ends, any remaining Breaths granted by it are lost. A target enlarged while unable to breathe does not gain these bonus Breaths.
• Natural Calculate the number of Breaths a creature has as normal. Then multiply the result by 2 for every Size larger than Medium.

Examples of Holding Your Breath

Let us look at practical examples of all these elements in action.

At 9th level, our delver has a Constitution modifier of +3 and a proficiency bonus of +4. Prior to recovering a sunken treasure, he paid a vestraadi to improve his ability to swim. He now has proficiency in Strength (Athletics) checks made to swim (or indeed hold his breath anywhere). How are his Breaths affected?

If our example delver is surprised or caught unaware, he gets 5 + his Constitution modifier (+3) for a total of 8 Breaths. However, with proper preparation, our example delver can hold his breath for much longer.

His breathing exercises mean he gets the standard minimum of 5 Breaths and adds to that the base 5 for Breathing in Deeply on the first round of preparation. His Constitution allows him to Breathe in Deeply 3 more times granting an additional 15 Breaths for a total of 25.

His vestraadi training also helps: as he is proficient in Strength (Athletics) checks made to swim, he gains an additional 10 Breaths (half his proficiency bonus x 5).

After all this preparation, our example delver has a total of 35 Breaths to use when recovering his treasure. As a Breath allows you to spend 1 round (6 seconds) in an environment in which you cannot usually breathe it means our example delver can be underwater for 35 rounds, or 3-and-a-half minutes. If our example delver was able to take advantage of an enlarge/reduce spell, he would add another 5 Breaths to this, making a total of 40 Breaths, or 4 minutes if he does not encounter any issues.

Meanwhile, Narguer the stone giant is exploring a methane-filled mine. She has a Constitution modifier of +5 and a proficiency bonus of +3. However, she adds double her proficiency bonus to Strength (Athletics) checks. How are her Breaths affected?

If Narguer is surprised, she gets 5 + the Constitution modifier maximum of +4 for a total of 9 Breaths.

But Narguer is used to preparing carefully when entering mines. As ever, she gets the standard minimum of 5 Breaths and adds to that the base 5 for Breathing in Deeply on the first round of preparation. Her Constitution allows her to Breathe in Deeply 4 more times granting an additional 20 Breaths for a total of 30.

In addition, as she gets double her proficiency bonus to Strength (Athletics) checks, she takes full advantage of her possible additional maximum Breaths, gaining 15 more (her proficiency bonus x5).

Finally, as Narguer is a Huge creature, her number of Breaths is quadrupled. Where does that leave her?

This means Narguer has a total of 180 Breaths to explore the mine, equivalent to 18 minutes. By Breathing in Deeply she can walk almost 3,600 feet into the unbreathable gas and back again, so long as she doesn’t face any problems!

Actions and Breaths

The Breath engine is based on a simple rule, which applies globally to actions taken: If it requires strenuous activity, it consumes a Breath. Movement consumes one Breath. Whenever a creature takes damage while holding their breath, they lose one Breath.

Trying to escape a grapple or taking the Attack, Dash, Disengage, Dodge, Help, Hide, Search, or Use an Object action consumes one Breath.

Bonus actions require special consideration, as they cover a variety of different things, ranging from mostly mental actions, which should not require an additional Breath, to physical assaults which should consume an extra Breath. The GM is the final arbiter of what consumes a Breath, and what doesn’t. For instance, a rogue can use a bonus action to Dash, which would obviously use a Breath, while other rogues can use a bonus action to look for a hidden creature, which would not use a Breath.

The Ready action is a special case as it is an action that sets up doing something as a reaction. Whether or not using the Ready action consumes a Breath is contingent on the type of action performed. If it is strenuous, it consumes a Breath, but if not, then it doesn’t. The Ready action only consumes a Breath; if the creature taking it actually does perform the action readied—the Breath is consumed upon performing the readied task, not when using the Ready action.

Reactions follow the same guidelines as bonus actions: if they are strenuous, they should consume a Breath; if they are not, then they shouldn’t. Executing an opportunity attack, for example, is strenuous, and should consume a Breath.

Suffocation

If a creature runs out of Breath, it breathes in whatever substance it finds itself in—water, gas, dust, a vacuum, and so on. If it is under water or within an unbreathable atmosphere, it begins dying and must make its death saving throw (DC 10 as usual) at the end of its next turn. This does not reduce the suffocating creature to 0 hit points—the creature can continue to struggle for air until it dies.

Unlike a regular death saving throw, the creature cannot become stable without Breath, regardless of how many death saving throws it successfully makes – it needs to reach air before it can lose its dying condition. Once a creature reaches air and manages to breathe, it loses the dying condition, but increases its exhaustion levels by +1, to a maximum of 5.

For each death saving throw beyond the first that a creature makes, the DC increases by 2. This stacks with itself, so, on the third death saving throw, a suffocating creature needs to succeed on a DC 16 death saving throw to continue struggling. The DC resets after the creature has taken a Breath.

If a suffocating creature takes damage from any source, this is treated as usual, but also increases the DC of the death saving throw by a further 2.

Variant Takes to Suffocation

Increased Importance of Constitution. If you wish, you can allow creatures to make a Constitution saving throw instead of a death saving throws to resist suffocating. Just use the same DC guidelines as above. This emphasizes the importance of being tough and makes the system less lethal.

Increased Importance of Strength (Athletics). If you wish, you can allow characters to roll Strength (Athletics) checks made to swim to resist suffocating, using the same DC guidelines as above. This emphasizes the expertise of being able to operate under pressure when faced with asphyxiation and makes the system less challenging.

Possible Use of Skill with Different Abilities: Constitution (Athletics). The rules for ability checks discuss the idea that a specific proficiency might reasonably apply to a different kind of check. In fact, swimming is the main example given in these guidelines. Therefore, the GM may wish to combine the variations suggested above and allow a player to apply their character’s proficiency bonus in Athletics to the Constitution check just as you would normally do for a Strength (Athletics) check.

Optional Variant Rule: More Attacks, Less Breath

If you want to further emphasize there source management aspects of Breaths, and/or the slower pace of air-breathing creatures under water, consider this variant rule: each attack executed consumes one Breath. This means that characters with the Extra Attack feature must decide on whether or not to use their additional attacks.

Spellcasting and Breath

Holding your Breath does not impede concentration.

Spells with either somatic (S) or material (M) components consume one Breath when casting them.

Spells with verbal (V) components are very hard or impossible to cast while holding your breath, depending on the GM’s decision. If you want to allow spells with verbal (V) components to be cast in your game while holding one’s breath, doing so should be hard and require a saving throw using the caster’s spellcasting ability (for example Charisma for bards) against a DC of 15 + the spell’s level. On a failure, the spellcasting attempt fails, and the spell slot is expended. Additionally, the character may or may not be exposed to the substance they are in, subject to the GM’s discretion. On a successful saving throw, the spell is cast. Regardless of success or failure, enunciating the mystic words costs the spellcasting creature a number of Breaths equal to 1 + twice the spell’s level (cantrips with verbal components cost 1 Breath). Attempting to cast a 3rd level spell, for example, would cost 7 Breaths. Spells with both verbal (V) and somatic (S) or material (M) components instead consume the Breaths required by their verbal (V) component. If a spell takes longer than one round to cast, the caster must successfully make the saving throw each round to continue casting the spell during the entire duration of the spellcasting process, and each round consumes Breaths as outlined above.

Optional Variant Rule: More Components, Less Breath

If you use the variant rule More Attacks, Less Breath, more components should also consume more Breath. In such a case, somatic (S) and material (M) components add their cost in Breaths together. If you choose to allow for verbal (V) casting while holding breath, the costs of somatic (S) and material (M) components should be added to those of the verbal (V) casting.

Conditions and Breath

Charmed. Attempting to convince a creature to breathe when the effect would be harmful to it causes the creature to cease considering you as friendly, thereby ending the effects of spells like charm person. In the case of stronger types of charm, such as dominate person, trying to make a creature stop holding their breath when doing so would be harmful to them grants them an immediate saving throw made with advantage against the effect. The dangerous action is only taken if the target fails its saving throw. For example, commanding a creature to cease holding its breath and breathe in hallucinogenic spores would only result in a loss of Breath and exposure to the spores if the creature failed its saving throw. Grappled. A grappled creature loses an additional number of Breaths at the end of its turn if it remains grappled. It loses an amount of Breaths equal to the difference between the grappling creature’s and grappled target’s contested check, up to a maximum of the grappling creature’s choice of either its Strength or Dexterity modifier, minimum 1. If the grappled target has failed its attempt to escape the grapple, it instead loses a number of Breaths equal to how much it failed its escape attempt against the escape DC, up to a maximum of the grappling creature’s choice of Strength or Dexterity modifier. An aboleth (Strength 21) squeezing the air out of a target creature could, for example, squeeze up to 5 Breaths out of a grappled creature each round.

• Paralyzed A paralyzed creature immediately loses all remaining Breaths held and begins dying at the end of its next turn.
• Petrified A petrified creature is made of stone and does not breathe. If it is de-petrified, it retains any Breaths held prior to being petrified. This would allow for a submerged character to self-petrify, leave a note for an aquatic ally to get them out, and then de-petrify them.
• Prone A creature forced prone, usually on land, loses one Breath if it gains the prone condition due to an effect or attack by a hostile creature. If it becomes prone of its own volition, it does not lose a Breath.
• Unconscious An unconscious creature immediately loses all remaining Breaths held and begins dying at the end of its next turn.

Special Actions and Considerations Regarding Breath

When using the Breath rules presented here, creatures can use several special actions.

• Gasp for Air. As a reaction to being grappled by a creature and/or being forced into a dangerous atmosphere, or as a reaction to starting the turn being grappled that can only be taken while within 5 foot of breathable air, a creature can Gasp for Air. This grants the creature 1 Breath.
• Share Breath. A creature can use the Help action (consuming 1 Breath) while within 5 foot of a friendly creature to Share Breath with it, usually by pressing their mouths on the mouth or equivalent thereof of the recipient, donating their choice of up 10 Breaths. For every 2 Breaths donated, the recipient receives 1 Breath. So, for 10 Breaths donated, the recipient would receive 5 Breaths.
• Accept Share Breath. A creature can use its reaction to an ally attempting to Share Breath to accept the Breath being shared. The recipient receives the amount of Breaths shared by the donor. Unless the GM decides otherwise, using the Accept Share Breath reaction does not consume Breath.

Taking a Breath from a Portable Air Source. A creature can take a Breath from a portable air source, such as an air bladder or the like, by taking the Use an Object action. This special Use an Object action does not consume a Breath, provided the source of air actually has breathable air. If the air is tainted, poisoned or otherwise compromised, the attempt does consume the usual 1 Breath.

Optional Rule: Live, Damn It!

If you want to decrease the deadliness of the rules presented here, consider the following. A creature that has asphyxiated has a grace period of one minute. If, during this time, it reaches air and is treated by a creature proficient with the healer’s kit, it has a chance of reviving. The creature using the healer’s kit gets a single DC 25 Wisdom check made with the healer’s kit. This check takes one minute of uninterrupted work. On a success, the suffocated creature revives at a stable 0 hit points and has 4 levels of exhaustion, unless it previously already had 5 levels of exhaustion. Subject to the GM’s discretion, frigid environments might increase the grace period after which a character may be revived.

Variation: Subject to the GM’s approval, Wisdom (Survival) can also be used to revive asphyxiated creatures.

Additional GM Considerations

Some features of creatures require additional consideration, as do some less common scenarios.

Common Creature Features

Amphibious. For amphibious creatures, the engine only becomes relevant when they are in an atmosphere they cannot breathe.

• Hold Breath A creature with the Hold Breath feature should calculate its Breaths as normal, then triple the result.
• Semi-Amphibious. Once the noted time has elapsed, the creature uses this engine as though it could not Breathe in Deeply—after all, it has used up the majority of its breathable medium.

Airborne Hazards

While the most common source of suffocation for adventurers is water, there are more components that can interact with this engine, namely airborne hazards such as spores and poisons. These do require some thought on part of the GM. First, consider the important question: “Does the gas or spore need to be inhaled, or does contact suffice to cause detrimental effects?”

If the respective hazard needs to be inhaled, application of the engine is straightforward. You can hold your breath, use Breaths, and so on. For contact-based gaseous hazards and the like, the GM should clearly communicate to the players that mere exposure can be dangerous—cloudkill is an example here. It is frustrating to hold your breath, walk into a cloud of spores, and then suddenly realize that your efforts were in vain.

Water-Breathing and Shared Breath

It does not make logical sense for a water-breathing creature to Share Breath with creatures breathing air; however, the mermaid’s kiss saving the drowning sailor is an established trope of fantasy literature. How this is handled is up to the individual GM.

Any Amphibious or Semi-Amphibious creature can freely Share Breaths with other creatures, provided they can breathe the medium they’re currently in and aren’t suffocating.

Thin Atmosphere. The rules presented by the system focus primarily on suddenly not being able to breathe at all. However, there is no reason why you cannot use it for thin atmospheres, oxygen-deprived mountaintops, or dungeons where a vacuum is slowly sucking the air out of the complex.

In such an instance, assume that all characters have Breathed in Deeply to their total maximum. Then, tweak the frequency in which Breaths are consumed according to your needs to represent that the characters can breathe—just not sufficiently. You could, for example, determine that the characters use a Breath every 10 minutes of regular activity, and make strenuous activity (such as carrying another character, or sacks of treasure) impose an additional cost of Breaths.

In this case, individual actions in combat should not incur a loss of Breaths—instead, every couple of rounds (or every single combat) should cost an amount of Breaths suitable for the environment. This way, you can simulate slow asphyxiation and longer explorations into slightly less inhospitable places.

Further Considerations

Can it Suffocate? While the rules are clear for some monsters like vampires and other undead, it makes sense to think about whether an unusual weird tentacled aberration and accompanying oozes can suffocate.

What if it Cannot Breathe Air? In the most common instance, this problem becomes relevant if the creature usually breathes water. In such a case, it makes sense to, e.g., substitute Strength (Athletics) checks made to climb and climbing speed in order to determine whether such creatures should be able to Breathe in Deeply beyond their standard quota, as climbing and swimming are both rather strenuous activities.

How Much Breath Should Portable Air Containers Hold? From a sea serpent’s swimming bladder to a simple leather-improvisation, or by chewing on magical corals, players are bound to have their characters make improvised air containers. As a general guidance, a good idea should yield more Breaths than a bad one.

The number of Breaths the party should be able to access ultimately depends upon the requirements of your story—characters need less air if they are just exploring some sunken rooms. However, if you plan an adventure in a fully submerged dungeon or perhaps the deep ocean, make sure the characters have a source of oxygen that will suffice for the exploration. Determine how much air they will need and provide accordingly. Why Use these Rules?

Why bother using the Breath engine at all? Because this rewards the player’s agency! It rewards those who act wisely, considering the expedition, environment, and careful use of their actions. To get the most out of the engine, it is suggested that virtually all gases and gas-like hazards use it as presented here. In addition, these guidelines add to its efficiency: Gas-like Spells and Innate Spell Abilities. When introducing the engine presented in conjunction with gas-based magic such as cloudkill or the spore-cerer’s spores, consider the following:

• If you make a gas such as cloudkill inhaled, consider doubling its damage caused when actually breathed in, as the party will have had plenty of chances to avert it.
• If you make features such as the spore-cerer’s spores inhaled, saving throws against them should be made at disadvantage. This also holds true for effects that are not based on damage.
• Also consider, particularly if the spores or gases originate from a character in the party, that not every creature will realize what is happening, or even perceive the effect. Be very careful with an option that tampers with the primary class feature of a class, as unlike a few gaseous spells, this modifies not just one weapon in the arsenal, but the entire arsenal. It is recommended that you make such features contact-based instead.

Handling Gas-like Hazards and Breath. A jungle of mushrooms shedding poisonous spores faces the party, and the members must hold their Breaths as they navigate from cap to cap through the dense shroud of deadly spores—that’s exciting, and in such an instance, the effects should be classified as inhaled. Consider using the deadlier columns on Table 11-5 if a character actually has to breathe in the spores.

If the environmental effect instead applies upon mere contact, and said contact cannot be avoided by the characters, it should, at most, use the least punishing columns of Table 11-5.

Use the character with the lowest potential of total Breaths as your guideline, but also make sure that you have some tasks and encounters that reward the character with the highest Breath capacity.

If the players try to cheat the system, remember that conventional air will float upwards, which can make navigation more difficult. Additionally, air containers can be destroyed or pierced.

On the Importance of Story. If one of the characters is, for example, a pearl diver by background, or has a siren or water weird in their ancestry, it’s easy to reward the character with additional capacity to hold Breaths, using the examples outlined above. A pearl diver by trade should probably calculate their Breaths available as though they had the Hold Breath feature.

By contrast, a character with a hacking cough might have the maximum amount of Breaths they can hold decreased until cured. Why bother if the Water Breathing Spell Exists? The engine applies beyond water. Secondly, water breathing can be dispelled, which is logically the first thing aquatic creatures should do if they encounter air-breathing invaders.

Repercussions of Implementing this System

This system is designed to make navigating half-sunken caverns more exciting, or to make an escape from a place sinking beneath the waves a memorable struggle. It can be used to simulate a frantic struggle from air pocket to air pocket in a variety of different circumstances, from partial cave-ins, to rising gases, to spaceships leaking air.

As is clearly evident, most creatures will have less time than when using the standard rules before they start suffocating, but unlike with the regular rules, they can keep struggling until the end, and aren’t relegated to just rolling their death saving throws and being bored while watching their fellow players enjoy the game.

Additionally, the system presented introduces teamwork and agency into diving, exploring spore-choked caverns, poisonous volcanic vents, and the like. The characters need to manage their Breaths, and the burly fighters get to help their less hardy compatriots.

It also lets the GM make dungeons more nuanced, and rewards the group for, at least sometimes, splitting the party. The barrel-chested barbarian can easily dive through a tunnel, but his sick warlock buddy and the feeble cleric may have some issues, so he has to take them along and Share Breath.

However, the G M should not jump on solo characters all the time. Most experienced players will be rather tense once they realize that the party must split, even if ever so briefly. Additionally, by calculating Breaths and distances accordingly, you can easily make subtle puzzle-adventures, where navigating a hostile environment requires some thought, experimentation, and planning.

Regardless of how you implement this system, be sure to communicate clearly to your players how it works and how you choose to interpret it in the context of your game. Start small, with a few submerged rooms or tunnels, and then build on that. Alternatively, perhaps run a few simulation scenarios with your players to see if everyone fully understands how the system works and if it is a good fit for your gaming group.

Tracking Breath

A popular way to track Breath is using small snacks—roasted peas, raspberries or blueberries or similar healthy food is recommended. Just eat the snack if you consume a Breath. In the absence of food, or if everyone is full, using trusty old counters, coins or dice is just as easy.

So, you’re doing a chapter about the hazards I’ve bested under the ground, eh? With all due respect, I think I’ve covered the basics extensively, but if you insist. Just remember, be alert, keep your eyes open, and use all your senses. More than once it has been my nose that tipped me off to the presence of some lethal menace lurking just around the bend!

I will stress the need to plan your equipment selection for the conditions you will face on your expedition. For example, the experienced delver always carries a coil of rope, but if you know that considerable climbing—up or down—will be required, consider carrying extra rope. Sturdy steel pitons, and a hammer to pound them into a stone-bound crack, can be lifesavers. A rope ladder is another readily portable object that can greatly facilitate a vertical traverse. Such a ladder can even be used to form a rudimentary (and quite possible terrifying!) bridge. Anchored by pitons, such 16 This is amusing in that most of our example delver’s associates attest to the fact that he is only a passing acquaintance of bathing when delving for any period of more than a few days, and that his pungency is often what caused foes to falter or flee rather than his fearsome appearance.

Once again our example delver’s not-exactly-terrible but hardly original advice is marred by an inexact recounting of his own experience. In fact, our Worthy Narrator was famed for his ability to fall asleep instantly when a party’s progress came to a halt. It was all his companions could do to keep his snoring to a minimum, and even in the event of a sudden attack out of the darkness, with shrieking goblins banging shields and charging from several directions.

If water obstacles are expected, make allowances for that. While bulky and somewhat heavy, a canvas boat can be transported by several sturdy delvers, with one carrying the fabric and others carrying the wooden struts of the frame. It may be that an expedition that would have been turned back by a lake or pool will find such a vessel just what is needed to allow progress to continue. And perhaps make a few allowances for its care.

When on the move, make sure you have a keen-eyed lookout in the forefront of your party, and another such bringing up the rear. If passing unknown spaces to either f lank, post a guard to protect your party against a surprise attack from the side. Finally, if you’re delving with companions and you need to stop for a rest, or even for a period of sleep, make sure that you don’t all fall asleep at once! Even though it left me weary and bleary on rising, I have spent many a rest stop keeping my eyes open through the long, quiet hours.

Let me add one further point of care: even if you are traveling with companions who can all see in the dark, don’t neglect the necessity of having some form of illumination—be it torch or lamp or at least f lint, tinder and steel—along with you. Often the denizens of the dark are even more sensitive to light than a dwarf or gnome who has spent an entire lifetime underground. The sudden f lash of aflame can, merely by its shocking visual burst of light, sometimes gain for one a significant, if momentary, advantage against such a creature.

Now I think of it, it might be best if you consider the implications of not preparing well for the hazards you might fall foul of—that ought to focus your mind rather than listening to some chandler trying to part you from your coin.

---

Underworld Hazards

Streamlined Overland Hazards

The exploration of the Underworld is not something for the foolish, meek or faint-hearted—even the plant life and insects can prove to be detrimental to the health of those unprepared for what the realms below hold. That being said, with the demands life has on the schedule of players in a game, it may not always be feasible to play out every single little encounter or event.

However, this may result in the wilds becoming mere backdrops for the main story, the aspect of survival being lost in the “heat of the moment”. The rules regarding units of stock obviously help when it comes to the depiction of survival in a hostile environment, but as deadly as the Underworld may be, it is not always a grueling hellhole that attempts to actively kill you; occasionally it is actually helpful.

As such, we propose an engine that establishes a means to retain the danger of the wilderness, while still allowing for a quick resolution of, for example, trips between dwarven holds or delivery of a message between Underworld druids. For this purpose, a classification of danger in a given region can fall among 6 danger levels. Danger may be mundane (such as treacherous terrain), magical or any combination deemed applicable by the GM. See Table 11-1 below for the details.

Each danger level features a DC—this DC may apply to a saving throw, a skill or ability check, a tool check, or anything that the GM considers to be valid. For example, if the party decides that having a colliatur guard to guide it through the colloid would be beneficial, it is suggested that a GM could use this DC for the haggling involved and apply for Charisma (Persuasion), Charisma (Intimidation), or another check that they deem to be suitable for such a context. On a failed check, the entire party (or single, random character, if it makes sense in the context) takes a fixed Terrain Damage Value (TDV), with the damage type corresponding to the terrain as the journey remains a grueling one.

Crossing a field of obsidian shards will cause slashing damage to all involved incapable of flight; braving steaming hot lava tubes may cause fire damage, and so on. It is important here to remember that this terrain damage can NEVER reduce a character below 1 hit point—the terrain is not intended to kill off characters in boring ways. Magic, of course, needs to be accounted for; with the right kind of utility magic available, the party may choose to expend spell slot levels to avoid taking the damage listed. The number of spell slot levels required per character to bypass the respective TDV is note on Table 11-1. These spell slot levels may be paid for in any combination feasible; paying the required amount of spell slots to prevent two characters from taking the TDV does not absolve the rest of the party from taking the damage indicated… Naturally, it is very easy to create even deadlier danger levels and customize the above—in a dead magic zone, the use of spell slots to bypass a TDV, for example, would obviously not be available. Depending on how gritty you want your campaign to be, it is generally recommended that you consider danger level Dangerous or Very Dangerous as the point where you should consider implementing the unit of stock survival rules. Any level above Remote is also where making camp should start to become more dangerous.

Beyond streamlining overland travel, the above allows you to think of cross-country treks in a more structured manner—for example, perhaps that guide the party hired WILL make the area less dangerous—making you apply the effects of a lesser danger level. Of course, the inverse could be true as well—a guide trying to lure the party into the (ant) lion’s den could increase the damage level for the wilderness trek. The DCs present valid guidelines to determine social interaction with the respective individuals, to notice being misled, and all other types of shenanigans that may occur. The GM should also bear in mind that the efforts of PCs and NPCs can directly alter the danger levels—a villain releasing monsters near a settlement may increase the danger level of a region. Similarly, heroes that pacify a region, slaying the big monsters, and so on, may decrease the danger level of a region.

The number of times the above hazards are actually encountered per day would be highly contingent on the area in question and the demands of the narrative—navigating a war-zone may result in encounters every hour or so, while more serene environments may only have such an encounter every 8 hours, or every day.

Table 11-1: Streamlined Overland Hazards

Danger Level	Description	DC	TDV – Terrain Damage Value	Spell slots Used per Character
Safe	Well-traveled roads, probably maintained by nearby settlements.	5-9	5	1 spell slot level for whole party
Rarely traveled	Travel by path/tunnel; rare patrols and/or monster activity. Chances of natural hazards. 10-13 11 1 spell slot level per character Remote Underdeveloped paths, trails of an expedition, forgotten road. Rarely, if ever patrolled by guards.	14-17	24	2 spell slot levels per character
Dangerous	Wilderness; alternatively, more civilized, but plagued by serious foes and hazards.	18-21	37	3 spell slot levels per character
Very Dangerous	Lethal landscapes, actively detrimental to survival; regions where humanoids are not supposed to tread.	22-25	51	4 spell slot levels per character
Lethal	No non-adventurer goes here; has an earned reputation of being deadly, wild, haunted and worse.	26-30+	64	5 spell slot levels per character

Underworld Hazard Generation

Before we discuss how to use hazards, we ought to define the term. For our purposes, a “hazard” is just about everything that is not a creature or a trap. A hazard does not (usually!) have an initiative, and may or may not use an attack of its own. Hazards may move or damage creatures, but typically are not a deadly threats, unless the character subjected to one has already been severely wounded. A pool of lava may be terrible to fall into, but unless there’s a need to get close to it—to cross a bridge, reach an island and advance on a foe emerging from it—the party can simply avoid it. Why Use Hazards?

There are plenty of reasons to incorporate hazards into encounters and your game.

Because It Makes Sense. Almost no encounter takes place in an undefined, gray hallway; in a fungal jungle, there will be myriad trunks, lianas, and spores around; in a dwarven bar, there will be chairs and tables, and potentially a fire pit, and so on.

To Alter the Difficulty.

Mechanically, you can use hazards to make encounters easier, more difficult, or simply more exciting. This ultimately depends on the pairing of monsters and hazards—pairing a vent of flammable gas with a water elemental may be potentially dangerous. Pair it with a fire elemental, and we have the constant potential for explosions.

Conversely, a party facing a foe with superb immunities and combat capabilities may use hazards to help them deal with the adversary—from flammable gas vents to deal with swarms, to steep cliffs to delay (at least temporarily) the nigh-unstoppable golem, there are plenty of ways for all involved to make combat more exciting. Some hazards will potentially allow the party to make area attacks, such as exploding sacks of acidic spores or kegs of volatile, explosive amber. Clever parties may use hazards employed by the enemy and turn the tables on them.

To Provide Meaningful Choices. This was already implied by the previous point. The characters can interact with the hazards in meaningful ways. One of the strong aspects of 5E is that is has rules for lair actions that render the region an encounter happens in matter more in a mechanical context. An easy way to enhance the choices available to the party in combat would be to associate lair actions with tangible things, where sensible, and allowing the characters to interact with them, if it makes sense. Hazards can be used to encourage characters to try new things in combat, and can similarly be used to discourage the party from using their standard tactics—a fighter who likes to lock down foes in melee might reconsider standing still if the mud is slowly swallowing him, and the warlock may think twice about throwing a firebolt in a series of tunnels filled with flammable gas.

Building Hazards

When creating new hazards for your encounters, ask yourself a few questions: What is it? The first thing to consider is what the hazard actually represents in the game world. Is it appropriate for the environment in which you place it, and does the context within which the party interacts with it make sense?

What does it do? While including dressing that has no mechanical effects can greatly add to the immersion of the roleplaying experience, for our purposes hazards should have a tangible mechanical effect. Here are several suggestions that should help you think in an ordered way about hazards. It should be noted that these general categories are only meant as a starting point. They can be combined, and we encourage GMs to expand the list.

Obstruction or Obfuscation. These are perhaps some of the most commonly encountered types of hazards around. As a rule of thumb, they get in the way of the characters, or hinder the ability of the characters to properly perceive their enemies. They can be difficult terrain, require checks to bypass [such as a Strength (Athletics) check to scale a pillar] or simply block the way (such as a portcullis); more common than these examples would be hazards that hamper the field of vision, such as mist, smoke or clouds of spores.

• Movement Alteration. Hazards don’t have to automatically be detrimental—steering your glider into pandemoniacal gusts of wind or diving into a particularly strong current may either move you automatically without requiring any exertion on your part or possibly slam you face-first into an obstruction. A means to simulate this type of scenario was presented earlier—the vessel momentum rules can account for this.
• Damage A hazard is most commonly used simply to deal damage to any creature that is affected by it or starts its turn in the area affected by the hazard. The damage type is obviously contingent on the nature of the hazard in question. Unless the hazard has an attack roll, it should have a saving throw, with half (or no) damage taken on a successful saving throw.
• Negative Conditions. Some hazards impose negative conditions on those exposed to them. These types affect characters either actively, or on the start of their turn while they are in the hazard’s area of effect. For example, rhizomes may attempt to restrain the characters, gas may blind them, and so on. As a general rule of thumb, there should be a means to escape the hazard or prevent its effects—a saving throw or an attack roll is obviously in order to mitigate the effects of most such hazards. Similarly, hazards that impose negative conditions should generally not prevent the characters from taking any actions—it is not particularly fun to wait around and hope to be able to act next turn. In the instances where such a scenario would be valid, where potentially crippling conditions may be incurred, it is strongly suggested that you make the onset a slow, creeping process—such as being gradually petrified by exposure to an area of elemental earth. As a benefit, this helps increase the tension and sense of urgency.
• Benefit The hazard actually provides a bonus to characters interacting with it or being adjacent to it. This might be something simple, like a minor boost to damage for a fighter swinging his sword through a pillar of scalding fire to hit a foe, an area attack (throwing a mushroom cap filled with poisonous spores), or the like.
• Healing Some hazards can provide limited healing when interacted with—sipping from a magical spring may reduce exhaustion, or even heal the characters. Perhaps a benevolent, symbiotic worm can cause the character to recover a limited number of hit point each round for several rounds.
• Special Abilities. Some hazards can bestow special abilities to the characters. These may be permanent in rare cases, but generally should be temporary. Bathing in the blood of a primal dragon may temporarily fortify the character against an element, and perhaps even allow the character to use a breath weapon a limited number of times—if they survive the experience, obviously.
• Combination As you can see from the various examples above, many hazards act as a combination of several effects.

Does the Hazard Change? Can it be Altered?

Most hazards remain the same during an encounter, and there is no intrinsic requirement for one to change—a field of razor-sharp obsidian flints won’t usually go out of their way to attack or change—unless some serious magic is involved. However, hazards that do change can make battles much more dynamic and, ultimately, more interesting. There are four basic ways of thinking about how a hazard interacts with the world in game.

• Activated On the battlefield, at the start of an encounter, this type of hazard has either a limited effect or none at all. The party or its opposition may activate the hazard to initiate its full effects, such as tampering with a lightning rod-type device to make it fire at random targets. Activating a hazard, unless otherwise noted, takes an Action. Methods of activation might include skill checks, sacrificing hit points, expending Hit Dice, or similar means, while some activated hazards may be set off more quickly or more slowly.
• Destroyable This hazard may be destroyable, which can end its effects, initiate its effects, or change its effects from the initial effect to a second one. To destroy a hazard this way, a sufficient amount of damage needs to be inflicted on it. This needs to bypass the damage threshold of the substance the hazard is made out of, if any, and in some cases it may take a specific damage type to destroy the hazard, or require that damage occurs to a sufficiently large area. Similarly, some sorts of hazard may require a skill check, use of Dexterity with thieves’ tools or similar actions to destroy, or an alternate way of dealing with the hazard in question. If the hazard occupies a larger area, the GM may deem it appropriate that sections must be destroyed individually—some hazards may only be destroyed in their entirety, while others allow for slow dismantling. For example, a gas vent that constantly belches forth noxious fumes will not be impeded by funneling away the gas, unless the vent itself is collapsed or shut in some manner.
• Triggered Triggered hazards change in some way as a response to another action—think of these basically as the hazard taking a reaction. This may happen when a creature enters a certain square, takes a type of damage (or enough of it), and the like. For example, an ahool temple may generate spell effects whenever enough blood is spilled.
• Random The hazard alters and/or affects targets randomly. The most prudent way to handle this is for the GM to simply roll a die at the end of a round to determine those affected and/or the types of effect in the following round. These effects can keep the party and foes guessing but are very volatile and should not be overused.

Some Considerations Regarding Triggered Hazards

The chances are that if you have been playing roleplaying games for a while, you once ran into a trap you just did not see coming. You crossed an invisible line, a trigger, and a previously undetectable, unseeable magical trap fried your character without warning or context. This is not fun, and it is indictment of how many bad adventures are out there that this practice has not been purged thoroughly from the RPG scene.

Traps that have “invisible lines” make sense in certain contexts, such as when handling the treasure chest of the villain, or when securing a sacred idol. In just as many cases, however, their placement makes no sense. How does this clan of dwarves navigate its own hold if there are traps everywhere? How does the wizard use his laboratory? In the latter case, the tired “It’s magic/a wizard did it!” excuse is often employed. This will, when used a couple of times, result in the rogue checking EVERYTHING out of a justified sense of paranoia, which, in turn, bogs down the game and is no fun for anyone. A simple practice helps make adventures fairer: telegraph your threats.

Mention that a tunnel is unexpectedly pristine, when the previous ones were strewn with rubble; mention a sense of unease or tingling sensation; include that dangerous mushroom in your description of the room; mention the stain that hints at dangerous mold. The black, oddly humanoid silhouettes in the flame-blasted room. For magical traps, include a type of crystal or pet in the thieves’ tools kit that can be used to detect the presence of magical traps in a rudimentary version: “I draw forth Binkles, my magic-sensitive space-hamster/my arkon crystal/my uvwyx bauble to look for magical traps!” is much more compelling than “I make a Perception check for traps.”

Ensuring that your traps and hazards make sense puts the skill where it should be—in the hands of the players. If they do not “read the signs”, they will suffer the consequences; failure and damage are the results of errors by the players, not the results of an unfortunate roll of the dice. This, in turn, allows you to make hazards—and traps, for that matter—deadlier.

As a GM, think for a second about the placement of traps and hazards; a gnomish smuggler ring, for example, may well have traps that target “taller” races, but that gnomes can simply walk under. If the party tried to inform itself about a complex or region, strew some hints of what is to come. Creatures captured alive may provide valuable intelligence, and scouting should reap tangible benefits for the party’s planning. Headless bodies or undead might provide hints for scything traps. This paradigm holds true for traps and hazards both. Of course, you can still have the secret door that the villain uses to try to escape, but, unless the party knows it is moving into a testing ground-type of dungeon to determine the “worth of the chosen”, neither traps nor hazards should be random. But even in that instance, doing some research before should yield a cryptic prophecy, an account of a survivor who failed to best the test, or something similar. For hazards, this can be particularly rewarding. As you play, you could, for example, slowly establish that a certain mushroom, when squeezed, generates a conical burst of dense spores that can be ignited into an impromptu flamethrower. It won’t be long until the party knows this mushroom by name—in subsequent encounters you can refer to it by name, and then watch the gears in the players’ heads spinning as they adjust their strategy. This also slowly establishes a believable ecosystem while you are playing, which can lead to adventures all of their own! That mushroom from the previous example? Better believe that the party will seek a way to weaponize them! Similarly, a particularly nasty gas may have the party look for alternative routes—or heighten tension, particularly if their opposition is immune to said gas…

This may all sound obvious, but fair placement and consistent effects are key factors for the rewarding use of traps and hazards; doing so will greatly enhance the enjoyment of the game for all involved.

Does the Hazard Move?

Most hazards will be stationary during battle, but not all of them will. Moving hazards may move on their own initiative in the initiative order, or at the end of a round, subject to the requirements of the GM. Shifting terrain encourages both the party and its opposition to move around the area, either to avoid being subjected to detrimental effects, or to follow beneficial ones.

• Moving Hazards. This hazard moves about the battlefield during the encounter. It might move along a defined path, move at random, or it might be attracted or repulsed by certain creatures, actions or objects. Necrotic sludge may, for example, be repulsed by holy symbols.
• Spreading This type of hazard starts in one area, and then grows wider as the combat progresses. It might spread a fixed amount each round or it may grow exponentially. Actions taken or not taken may influence whether or not the hazard spreads—for example, channeling necrotic energy into the aforementioned sludge may cause it to spread at twice the rate, while blasting it with radiant damage may limit its expansion or even cause it to contract. Two prime examples are fire spreading and rapidly-growing ectotherms such as brown mold.
• Portable Hazard. This type of hazard does not move on its own, but it may be directed or moved around. This may or may not require an action, the use of a skill check, or magic. Several class features, such as the path of the fungal hulk’s Verdant Path feature (Underworld Races & Classes, page 96), or the slaver of the damned’s Dregs of Hel feature (Occult Secrets of the Underworld, page 38), may be classified as such a form of hazard. Reactive Hazard. Reactive hazards are similar to portable hazards, in that creatures on the battlefield influence how the hazard moves, but not by acting on it directly. Instead, the hazard responds to what happens, such as suffering a particular kind of damage or being affected by some kind of spell. Since this reaction should be consistent, it allows the hazard to be used by the party as an additional threat, as a tactical edge, or a combination of both.

Building Your Own Hazards

Step 1—Establish the Hazard Budget. First, add the average character level to the average proficiency bonus of the characters and round down, if required. This sum is the total base Hazard Budget (HB) (Table 11-2) you use to purchase effects for the level of hazard you wish to set up (Table 11-3).

Step 2—Determine the Basic Hazard Properties. What is the hazard supposed to be doing? Options generally come in 3 types: attack, movement, other.

• Attack This special ability lets the hazard attack and/or be used to attack one or more targets. They often require an action, but some may be usable as a bonus action or even as a reaction. These are the most complex to create.
• Movement Movement hazards provide or hamper forms of movement, such as swinging on a rope, flying on currents, and so on—as noted before, using the vessel momentum engine handles these types of hazards well.
• Other Anything that does not fall into either of the above categories, such as buffs to attack rolls, healing, gaining temporary resistance to a damage type and the like.

Step 3—Determine the Attack Roll and/or Save DC, if any. Determine the category of threat of the hazard. There are 4 categories of threat—minor, moderate, major and severe (Table 11-4).

Table 11-2: Base Hazard Budget by Level

Level	Base Hazard Budget (HB)
1	3
11	15
2	4
12	16
3	5
13	18
4	6
14	19
5	8
15	20
6	9
16	21
7	10
17	23
8	11
18	24
9	13
19	25
10	14
20	26

Table 11-3: Threat Level and Hazard Budget Costs

Threat level	Total HB-Cost (Cost to upgrade from the previous threat level)
Minor	0 HB (0 HB)
Moderate	3 HB (3 HB)
Major	8 HB (5 HB)
Severe	15 HB (7 HB)

Table 11-4: Hazard Attack Bonuses and Saving Throw DCs by Level and Severity of the Threat

Level of Hazard	Minor Attack Bonus	Moderate Attack Bonus	Major Attack Bonus	Severe Attack Bonus	Minor Saving Throw DC	Moderate Saving Throw DC	Major Saving Throw DC	Severe Saving Throw DC
1	+1	+2	+3	+5	11	12	15	16
2	+3	+4	+5	+7	12	13	15	16
3	+3	+4	+5	+7	13	14	15	16
4	+4	+5	+6	+8	14	15	16	17
5	+4	+5	+6	+8	14	15	16	17
6	+5	+6	+7	+9	15	16	17	18
7	+5	+6	+7	+9	16	17	18	19
8	+6	+7	+8	+10	17	18	19	20
9	+6	+7	+8	+10	17	18	19	20
10	+7	+8	+9	+11	18	19	20	21
11	+7	+8	+9	+11	18	20	21	22
12	+8	+9	+10	+12	19	21	22	23
13	+8	+9	+10	+12	19	21	22	23
14	+9	+10	+11	+13	20	22	23	24
15	+9	+10	+11	+13	20	23	24	25
16	+10	+11	+12	+14	21	24	25	26
17	+10	+11	+13	+15	21	24	25	26
18	+11	+12	+13	+15	22	25	26	27
19	+11	+12	+14	+16	22	25	26	27
20	+12	+13	+15	+17	23	26	27	28

Table 11-5: Base Damage Caused

Level	Minor Damage	Moderate Damage	Major Damage	Severe Damage	Minor Saving Throw DC	Moderate Saving Throw DC	Major Saving Throw DC	Severe Saving Throw DC
1	3 (1d6)	4 (1d8)	5 (2d4)	7 (2d6)	11	12	15	16
2	4 (1d8)	5 (2d4)	7 (2d6)	7 (3d4)	12	13	15	16
3	5 (2d4)	7 (2d6)	7 (3d4)	9 (2d8)	13	14	15	16
4	7 (2d6)	7 (3d4)	9 (2d8)	10 (4d4)	14	15	16	17
5	7 (3d4)	9 (2d8)	10 (4d4)	11 (1d20)	14	15	16	17
6	9 (2d8)	10 (4d4)	11 (1d20)	11 (2d10)	15	16	17	18
7	10 (4d4)	11 (1d20)	11 (2d10)	13 (2d12)	16	17	18	19
8	11 (1d20)	11 (2d10)	13 (2d12)	13 (3d8)	17	18	19	20
9	11 (2d10)	13 (2d12)	13 (3d8)	16 (3d10)	17	18	19	20
10	13 (2d12)	13 (3d8)	16 (3d10)	19 (3d12)	18	19	20	21
11	13 (3d8)	16 (3d10)	19 (3d12)	22 (4d10)	18	20	21	22
12	16 (3d10)	19 (3d12)	22 (4d10)	26 (4d12)	19	21	22	23
13	19 (3d12)	22 (4d10)	26 (4d12)	27 (5d10)	19	21	22	23
14	22 (4d10)	26 (4d12)	27 (5d10)	32 (5d12)	20	22	23	24
15	26 (4d12)	27 (5d10)	32 (5d12)	35 (10d6)	20	23	24	25
16	27 (5d10)	32 (5d12)	35 (10d6)	38 (11d6)	21	24	25	26
17	32 (5d12)	35 (10d6)	38 (11d6)	42 (12d6)	21	24	25	26
18	35 (10d6)	38 (11d6)	42 (12d6)	45 (13d6)	22	25	26	27
19	38 (11d6)	42 (12d6)	45 (13d6)	49 (14d6)	22	25	26	27
20	42 (12d6)	49 (14d6)	52 (15d6)	56 (16d6)	23	26	27	28

Having a minor attack bonus, save DC or causing minor damage does not cost Hazard Budget, but upgrading a component does cost HB. Consult Table 11-3 for the total HB-costs to the desired threat level. For your convenience, the costs to upgrade to the threat level from the previous threat level are provided in brackets.

Once you have determined the desired threat level, consult Table 11-4 to determine attack rolls or save DCs of the hazard’s effects. For your convenience, a general level rating has been provided. This level rating corresponds to the level of the party.

Step 4— Determine the Damage Caused (if any). Now that you have determined the threat level, attack bonus and save DC, if present, determine the base damage caused using Table 11-5, as well as its type. Note that, unlike traps, the damage values of hazards has intentionally been kept at a comparatively low level. Remember, not all damage is equal! Some damage-types are more “valuable” than others, as fewer creatures are immune or resistant to them. Table 11-6 is a list of damage types and suggested Hazard Budget-costs for them.

Step 5— Determine the Damage Frequency. Think about whether the base damage determined is recurring or a one-off instantaneous effect. If it is damage that can be inflicted multiple times by the hazard, use the value determined on Table 11-5: Base Damage Caused. If the damage may only be incurred once and/or represents a particularly deadly effect, consider doubling the number of dice rolled per entry. If the damage should only be incurred every couple of rounds, or you require a similar balancing tool, consider using a recharge mechanic, as appropriate for your specific hazard. For some ideas to price recharge, consult Table 11-7.

Step 6—Determine Area of Effect. This step requires the most contemplation, but at the same will be simple. Since you already know the type and form of the hazard and what it is supposed to do, you also know the shape that the hazard’s area of effect will take. Since there are many shapes, diameters, and the like that an effect might assume, and since overly large areas of effect may be detrimental to the opposition of the party as well, we propose thinking of area of effect as 3 rough categories.

Table 11-6: Hazard Budget—Cost by Damage Type

Damage Type	HB-Cost
Bludgeoning, slashing, piercing	None*
Acid, cold, fire, lightning	None
Necrotic, radiant, thunder	1
Psychic	2
Force	3

* If the damage is supposed to be treated as though from a silvered weapon, the cost is 1 HB instead of none; for adamantine or similar materials, the HB-Cost is 2 instead of none. Alternatively, decreasing the damage caused by one step on the Table: Base Damage Caused allows the damage type to be increased by one step. For further decreases in die-size below 1d6, use the following progression:

1d6 > 1d4 > 1d3 > 1d2 >1

Table 11-7: Hazard Budget—Cost by Frequency

Frequency	Cost in HB
Once	None
Recharges after a Short or Long Rest	None
Recharge 6	2
Recharge 5—6	3
Recharge 4—6	4
Recharge 3—6	5
Every Round	6

Alternatively, decreasing the damage caused by one step on the Table: Base Damage Caused allows the frequency indicated to be increased by one step. For further decreases in die-size below 1d6, use the following progression:

1d6 > 1d4 > 1d3 > 1d2 >1

Small: This area of effect is localized, e.g. a 15-foot cone or a 5-foot radius sphere. Suggested HB-cost: 1.

Medium: This is one step larger, such as a 60-foot cone or a 20-foot radius sphere. Suggested HB-cost: 2.

Large: Any area of effect larger than Medium. Suggested HB-cost: 4.

Step 7—Determine the Conditions Caused (if any). Table 11-8 is not a comprehensive list, as this would necessitate accounting for any and all modifications of base statistics. In order to provide a valid guideline for the GM, the table gives suggested HB-costs for the most commonly encountered condition.

Step 8—Determine the Frequency of Saving Throws Needed to Shake Off the Condition. How often do the affected creatures have to successfully make their saving throw to shake off the condition? When do they get to save again? Table 11-9 lists the HB-cost of various options.

Working through this process means you should have a good idea of how to make a variety of interesting, challenging hazards. These are rough guidelines, so do not feel constrained by them! Having hazards consume units of stock, modify momentum and similar tricks are very much possible! This engine is intended to be a broad protocol, not a prescriptive tool. If your players are particularly adept at making powerful characters, you can tweak any of the values provided.

Table 11-8: Hazard Budget—Condition Costs

Condition Name	HB-Cost
Blinded	2
Charmed	2
Confused (as per confusion)	3
Deafened	1
Fatigued	4
Frightened	1
Grappled	0
Incapacitated*	5
Invisible 0** Paralyzed*	6
Petrified*	7
Poisoned	1
Prone	0
Restrained	4
Stunned*	5
Unconscious*	7

*This condition should only apply after multiple consecutive failed saving throws against the hazard. Being taken out of the battle due to one failed roll can be frustrating.

**If the hazard turns enemies invisible, but does not affect the party, this should have a HB-cost of 2.

Table 11-9: Hazard Budget—Shake Off Costs

Shake Off	HB-Cost
Condition automatically ends the next round	0
Saving throw at advantage the next round to end the condition	1
Saving throw the next round to end the condition	2
Saving throw at advantage if the condition requirement (e.g. acting against ethos/attacking allies) is met	3
Saving throw if the condition requirement (e.g. acting against ethos/attacking allies) is met	4
Saving throw the next minute to end the condition	5
Saving throw after a short rest to end the condition	6
Saving throw after a short rest to end the condition, but it costs one Hit Die	6
Saving throw after a day to end the condition	7
Permanent, no further saving throw	10
Two consecutive successful saving throws required to shake off the condition	3
Three consecutive successful saving throws required to shake off the condition	10

Customizing the Hazards Generator

As you may have noticed, the default hazards generator engine is designed with a couple of goals in mind. It is made to result in reliable hits and failed saves even against optimized characters but has a comparably low damage output. This is fully intentional, in line with the whole “help the party survive and the players have fun” mantra. It also seeks to account for the more potent character options available out there and to present a serious challenge to the party. In short, the default engine is meant to help design hazards that the party is incentivized to use or avoid, not to annihilate them. Consequently, being exposed to them should be the result of the party’s decisions (or flawed tactics), not something that just happens with no way to avoid. While the damage output is nothing a character of the respective level cannot handle, even specialists should think twice before exposing themselves to such hazards.

This use of the engine does require some restraint with the nastier conditions. It is rewarding for parties that enjoy thinking on their feet and results in combat scenarios rewarding tactics and clever thinking over brute-forcing an encounter. Ideally, this makes everyone focus more on roleplaying, and treating hazards less as a floating damage area.

Different parties have different power-levels and preferences, though—5E does allow for a wide variety of different playstyles, and as such, you may opt for damage that is less punitive. If you want your hazards to be more of a nuisance, and less of a combat-defining component, or if you want a hazard to be harder to avoid without making its inclusion unfair, consider using the information in Table 11-10. It still should yield a challenge, but de-emphasizes the need to avoid hazards and makes even non-specialists capable of resisting the effects of hazards with a reliable frequency—in short, it provides a more lenient experience that is closer to how many published adventures handle hazards.

Table 11-10: Less Challenging Hazard Attacks Bonuses and Saving Throw DCs by Threat Level and Severity of the Threat

Level Minor Attack Bonus Moderate Attack Bonus Major Attack Bonus Severe Attack Bonus Minor Saving Throw DC Moderate Saving Throw DC Major Saving Throw DC Severe Saving Throw DC
1	+0	+1	+2	+3	5	8	12	14
2	+0	+1	+2	+3	5	8	12	14
3	+1	+2	+3	+4	8	10	13	15
4	+1	+2	+3	+4	8	10	13	15
5	+2	+3	+4	+5	10	12	14	16
6	+2	+3	+4	+5	10	12	14	16
7	+3	+4	+5	+6	10	12	14	16
8	+3	+4	+5	+6	12	13	15	17
9	+4	+5	+6	+7	12	13	15	17
10	+4	+5	+6	+7	12	13	15	17
11	+5	+6	+7	+8	13	14	16	18
12	+5	+6	+7	+8	13	14	16	18
13	+5	+6	+7	+8	13	14	16	18
14	+6	+7	+8	+9	14	15	17	19
15	+6	+7	+8	+9	14	15	17	19
16	+6	+7	+8	+9	14	15	17	19
17	+7	+8	+9	+10	15	16	18	20
18	+7	+8	+9	+10	15	16	18	20
19	+7	+8	+9	+10	15	16	18	20
20	+8	+9	+10	+11	16	17	20	22

Similar concerns apply when it comes to base damage caused—Table 11-11 provides a greatly toned down damage output that you might consider using when creating a hazard with nasty conditions, one that can’t be properly bypassed by clever players, or when simply wanting to de-emphasize the effects of hazards on combat.

Optional Rules: Caps for Saving Throw DCs

As noted before, Table 11-4 accounts for optimized characters and specialists. While creating a character that can reliably meet the high-level hazard saving throw DCs proposed in that table is not difficult, the default values assume that it’s usually a bad idea for an entire party to enter a hazard—a rogue might be capable of avoiding the danger, but the same does not necessarily hold true for the wizard or the fighter. The default table is clearly designed to test even high-level specialists in their field of excellence, and some groups may balk at the prospect of not everyone having a chance to avoid a given hazard. While the Table 11-10 provides a more forgiving alternative, there is a chance that your group prefers the deadlier regular table, but not the high saving throw DCs. Perhaps you prefer the default table, but do not enjoy this particular component. If your group prefers dangerous hazards, but wants lower saving throw DCs, simply apply hard caps to the DCs, as shown on Table 11-12. Implementing these hard caps makes the hazard saving throw DCs plateau at higher levels, but still keeps them more significant than the DCs proposed in the less challenging table.

It should be noted that the whole system is designed to be modular—you could, for example, use the Less Challenging table’s lower attack bonuses and the damage values of the default table to represent a devastating hazard that hits more unreliably. It is your system, so make it your own! Table 11-11: Light Version of Base Damage Caused Level Minor Damage Moderate Damage Major Damage Severe Damage Minor Saving Throw DC Moderate Saving Throw DC Major Saving Throw DC Severe Saving Throw DC112 (1d4)3 (1d6)4 (1d8)58121421 (1d3)2 (1d4)3 (1d6)4 (1d8)58121431 (1d3)3 (1d6)4 (1d8)5 (1d10)810131542 (1d4)3 (1d6)4 (1d8)5 (1d10)810131552 (1d4)4 (1d8)5 (1d10)6 (1d12)1012141663 (1d6)4 (1d8)5 (1d10)6 (1d12)1012141673 (1d6)5 (1d10)6 (1d12)9 (2d8)1012141684 (1d8)5 (1d10)6 (1d12)9 (2d8)1213151794 (1d8)6 (1d12)9 (2d8)11 (2d10)12131517105 (1d10)6 (1d12)9 (2d8)11 (2d10)12131517115 (1d10)9 (2d8)11 (2d10)13 (2d12)13141618126 (1d12)9 (2d8)11 (2d10)13 (2d12)13141618136 (1d12)11 (2d10)13 (2d12)13 (3d8)13141618149 (2d8)11 (2d10)13 (2d12)13 (3d8)14151719159 (2d8)13 (2d12)13 (3d8)16 (3d10)141517191611 (2d10)13 (2d12)13 (3d8)16 (3d10)141517191711 (2d10)13 (3d8)16 (3d10)19 (3d12)151618201813 (2d12)13 (3d8)16 (3d10)19 (3d12)151618201913 (2d12)16 (3d10)19 (3d12)22 (4d10)151618202016 (3d10)19 (3d12)26 (4d12)32 (5d12)16172022

Table 11-12: Capped Saving Throw DCs

Saving Throw Type	Minor Moderate Major Severe DC Cap
15	18	22	25