Slaughtermaw Lamprey

Large beast, unaligned

Armor Class 16 (natural armour)
Hit Points 210 (20d10+100)
Speed 15 ft., swim 60 ft.

23 (+6) 18 (+4) 20 (+5) 2 (-4) 16 (+3) 12 (+1)

Saving Throws Str +10, Con +9
Skills Athletics +10, Perception +7
Damage Immunities cold
Senses darkvision 60 ft., passive Perception 17
Challenge 10 (5,900 XP)

Special Traits

  • Feed. The slaughtermaw lamprey is nourished by blood. Every time a slaughtermaw lamprey causes damage to a Medium or larger creature that has blood or an equivalent substance with a bite, it regains 27 (6d8) hit points.
  • Vanishingly Quick. The slaughtermaw lamprey is such a swift and agile swimmer that, whilst underwater, its movements do not provoke opportunity attacks.


  • Multiattack. The slaughtermaw lamprey makes three attacks, two with its bite and one with its stinger slam.
  • Bite. Melee Weapon Attack: +10 to hit, reach 15 ft., one target. Hit: 28 (4d10 + 6) piercing damage. If the target is a creature, it must succeed on a DC 17 Constitution saving throw or have its hit point maximum reduced by an amount equal to the damage taken. The target dies if this attack reduces its hit point maximun to 0. The reduction lasts until removed by the greater restoration spell or other magic.
  • Stinger Slam. Melee Weapon Attack: +10 to hit, reach 10ft., one target Hit. 17 (2d10 + 6) bludgeoning damage and the target must succeed on a DC 17 Constitution saving throw or be paralyzed for 3 (1d4+1) rounds. The target may repeat the saving throw at the end of each of its turns, on a success the condition ends.
    • Shattering Fangs. The slaughtermaw lamprey has a vicious bite of tough, razor-sharp teeth, fully capable of penetrating the thickest of hides or armors. If both the slaughtermaw lamprey’s bites hit the same creature, the slaughtermaw lamprey may, as a bonus action, also apply the damage of the second bite to the target’s armor or shield, if any. The armor takes a permanent and cumulative -1 penalty to the AC it offers for every 10 points of damage the slaughtermaw lamprey’s bite inflicts on it. Armor reduced to an AC of 10, or shields that drops to a +0 bonus, are destroyed. The creature no longer gains any benefit from the armor, but subject to GM’s approval, the shredded remnants of magic armor or shields may be reforged by a master smith. Though exceptionally dangerous, some hunt the slaughtermaw lamprey to render its oil and capture its eggs, as both are highly prized by alchemists.
    • Dried Slaughtermaw Eggs: When raw slaughtermaw lamprey eggs are quickly dried and eaten, the toxins in the eggs cause the user to experience intense feelings of euphoria, coupled with feelings of greater strength and stamina than normal in oneself. However, this takes its toll on the user’s mind, causing them to make progressively poorer decisions and can lead to periods of aggression or confusion with overuse. For 3 (1d6) hours after consumption the creature gains advantage on Charisma (Intimidation) checks, and if they possess the barbarian’s Rage feature, they gain two extra uses of it while this effect of consuming dried slaughtermaw eggs persists. However, for 6 (1d12) hours the creature is belligerent, constantly picking fights with other creatures, has poor impulse control, and has disadvantage on Wisdom (Perception) checks. With subsequent uses the danger of suffering a mental breakdown increase: Whenever a creature consumes more than one dose of dried slaughtermaw eggs per week, the creature must pass a DC 14 Charisma saving throw at the end of the period of poor impulse control or obtain a random long-term madness (as described in the 5E SRD). For each use of this drug, the DC increases by a cumulative +1. This resets only if a user has not consumed dried slaughtermaw eggs for a whole month. Price 1,800 gp.
    • Slaughtermaw Oil: Refined from the fatty tissues of slaughtermaw lampreys, this oil is quite sticky and highly flammable, creating a noisome green fire when burned. Torches and lanterns can burn this alongside their normal fuel to double how long they last. Additionally, it can be combined with alchemist’s fire to create a hotter and longer lasting fire. When slaughtermaw oil is added to a flask of alchemist’s fire increase the fire damage of the alchemist fire by 2 (1d4) and increase the DC of the Dexterity check to extinguish the flames to 12. Additionally, alchemist’s fire treated with slaughtermaw oil can be used underwater. Price: 5 gp.


The slaughtermaw lamprey is a long, scale-less fish that superficially resembles a jawless eel with many rows of barbed teeth and poisonous spines along their tail fins. Slaughtermaw lampreys are well acclimated to the icy waters and crushing depths of the ocean trenches of Orbis Aurea when they are adults, but they have to travel vast distances to create nests for their eggs, which must be laid in the shallow coastal regions to survive. Adult slaughtermaw lampreys remain to protect their eggs, but typically travel back to the depths after their eggs hatch, abandoning their young. After hatching, young slaughtermaw lampreys burrow into the sediments along the coast to filter feed for several months until they enter a metamorphosis to become adults. When the slaughtermaw lampreys finally emerge from their metamorphosis, they quickly seek out deeper waters to find suitable prey.

Savage Sea-hunter. Whether feeding on sea life in the deepest ocean trenches or nesting in the shallows along the world’s temperate coasts, the slaughtermaw lamprey is a fearsome predator that inspires fear and respect in seafarers and landdwellers alike. While stories of megalodons, giant squid, and whales tend to be more prevalent, those who have encountered a slaughtermaw lamprey while at sea spin harrowing tales of survival against one of the harsh planet’s most voracious hunters. Despite being jawless, a slaughtermaw lamprey’s powerful bite can pierce through even the toughest of hides and sailors speak of a slaughtermaw lamprey’s bite being capable of sinking waterborne craft as they tear through hulls seeking a meal. Slaughtermaw lampreys seem to fear no creature and many a sea creature has been seen sporting the ringshaped scars left by their attacks. Fortunately, slaughtermaw lampreys are rare during most of the year, only coming into contact with humanoids during their mating season when they venture from the icy depths to shallower coastal regions. A slaughtermaw lamprey can grow to reach an impressive fifteen feet in length and typically weigh about nine hundred pounds.

Slaughtermaw lampreys typically live ten to fifteen years, though older (and frighteningly, larger) members of their species are a part of many seafaring tales.

Deep Diver. A slaughtermaw lamprey spends much of its time feeding within the ocean trenches or along the ocean floor, attacking squids, sharks, and whales that swim by them. Typically, slaughtermaw lampreys prey upon whales, but they do attack larger predators such as megalodons and giant squids alone. Rare occurrences of multiple slaughtermaw lampreys feeding and hunting together to bring down larger prey is the stuff of nightmares. While squids can easily fight back, whales and sharks have a harder time defending themselves against even a solitary slaughtermaw lamprey. Both whales and sharks will often rise to the surface quickly, which typically causes the lamprey to detach as the rapid pressure change causes them to become confused and disorientated.

Light-Eater. Slaughtermaw lampreys have a habit of seeking out anything that radiates bright light or warmth, which some species of predators have turned into an advantage, such as the notorious deeplight hungerer, which utilizes bright glowing lures to attract them in the darkness of the deepest trenches.

Given enough time to adapt, they can rise to the surface to hunt, but it must be done slowly. While they focus on larger prey that can give them a larger meal, they have been known to attack smaller prey on occasion during their mating season, when they congregate along the shore and come into contact with humanoids and giants. Ships are particularly vulnerable as they resemble whales to slaughtermaw lampreys, and their teeth can easily puncture through armored hulls. As a ship begins to take on water, slaughtermaw lampreys will feast upon anything that tries to swim to safety, or in the case of larger ships swim inside the flooded cabins to snatch up stragglers.

Legendary Sea Monsters. A mixture of fear and reverence surrounds the slaughtermaw lamprey and some cultures have elaborate rituals around interacting with them. Some giant clan believe that within each lamprey is the soul of a powerful warrior who died outside of battle, destined to hunger for glory and bloodshed but never quite sating urges they no longer understand. Despite a rather gruesome coming-of-age ritual involving stealing lamprey eggs from a nest guarded by two mated lampreys, several more traditions exist to honor the lampreys, including blood sacrifice and offerings of live food. Artifacts originating from hill and stone giants, such as scrimshawed whale bones and shells depicting great battles or attacks made by lampreys and other creatures, can be found across coastal regions where lampreys can be found.

Section 15: Copyright Notice

Sea Monsters (5E) © 2021, Legendary Games; Authors Michael Ritter, Michael “solomani” Mifsud, Robert J. Grady, Mark Hart, Jeff Ibach, Alex Riggs, Scott D. Young, Jeff Lee, Matt Kimmel, and Jason Nelson.

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