Nihileth

Family: Aboleth

Large undead, chaotic evil

Armor Class 17 (natural armor)
Hit Points 135 (18d10 + 36)
Speed 10 ft., swim 40 ft., fly 40 ft. (ethereal only)

STR	DEX	CON	INT	WIS	CHA
21 (+5)	9 (-1)	15 (+2)	18 (+4)	15 (+2)	18 (+4)

Saving Throws Con +6, Int +8, Wis +6
Skills History +12, Perception +10
Damage Resistances acid, fire, lightning, thunder (only when in ethereal form); bludgeoning, piercing and slashing from nonmagical attacks
Damage Immunities cold, necrotic, poison; bludgeoning, piercing and slashing from nonmagical attacks (only when in ethereal form)
Condition Immunities charmed, exhaustion, frightened, grappled, paralyzed, petrified, poisoned, prone, restrained
Senses darkvision 120 ft., passive Perception 20
Languages Deep Speech, telepathy 120 ft.
Challenge 12 (8,400 XP)

SPECIAL TRAITS

• Aboleth Traits. Unless noted otherwise or where contradicted below, a nihileth has the same traits as a living aboleth. This includes legendary actions and lair actions.
• Undead Nature. A nihileth does not require air, food, drink, or sleep.
• Undead Fortitude. If damage reduces the nihileth to 0 hit points, it must make a Constitution saving throw with a DC of 5 + the damage taken, unless the damage is radiant or from a critical hit. On a success, the nihileth drops to 1 hit point instead.
• Dual State. A nihileth exists upon the Material Plane in one of two forms and can switch between them at will. In its material form, it has resistance to damage from nonmagical attacks. In its ethereal form, it is immune to damage from nonmagical attacks. The creature’s ethereal form appears as a dark purple outline of its material form, with a blackish-purple haze within. A nihileth in ethereal form can move through air as though it were water, with a fly speed of 40 feet.
• Void Aura. A nihileth doesn’t secrete the mucous cloud of an aboleth. Instead, the undead nihileth is surrounded by a chilling cloud. A living creature that starts its turn within 5 feet of a nihileth must make a successful DC 14 Constitution saving throw or be slowed until the start of its next turn. In addition, any creature that has been diseased by a nihileth or a nihilethic zombie takes 7 (2d6) cold damage every time it starts its turn within the aura.
• Infecting Telepathy. If a creature communicates telepathically with the nihileth or uses a psychic attack against it, the nihileth can spread its disease to the creature. The creature must succeed on a DC 14 Wisdom save or become infected with the same disease caused by the nihileth’s tentacle attack. This ability replaces an aboleth’s Probing Telepathy ability.

ACTIONS

• Multiattack. The nihileth makes three tentacle attacks or three withering touches, depending on what form it is in.
• Tentacle (material form only). Melee Weapon Attack: +9 to hit, reach 10 ft., one target. Hit: 12 (2d6 + 5) bludgeoning damage. If the target creature is hit, it must succeed on a DC 14 Constitution saving throw or become diseased. The disease has no effect for one minute; during that time, it can be removed by lesser restoration or comparable magic. After one minute, the diseased creature’s skin becomes translucent and slimy. The creature cannot regain hit points unless it is entirely underwater, and the disease can be removed only by heal or comparable magic. Unless the creature is fully submerged or frequently doused with water, it takes 6 (1d12) acid damage every 10 minutes. If a creature dies while diseased, it rises in 1d6 rounds as a nihilethic zombie. This zombie is permanently dominated by the nihileth.
• Withering Touch (ethereal form only). Melee Weapon Attack: +8 to hit, reach 10 ft., one creature. Hit: 14 (3d6 + 4) necrotic damage.
• Form Swap. As a bonus action, the nihileth can alter between its material and ethereal forms at will.
• Tail Action. Melee Weapon Attack: +9 to hit, reach 10 ft. one target. Hit: 15 (3d6 + 5) bludgeoning damage.
• Enslave (3/day). The aboleth targets one creature it can see within 30 feet of it. The target must succeed on a DC 14 Wisdom saving throw or be magically charmed by the aboleth until the aboleth dies or until it is on a different plane of existence from the target. The charmed target is under the aboleth’s control and can’t take reactions, and the aboleth and the target can communicate telepathically with each other over any distance. Whenever the charmed target takes damage, the target can repeat the saving throw. On a success, the effect ends. No more than once every 24 hours, the target can also repeat the saving throw when it is at least 1 mile away from the aboleth.

REACTIONS

• Void Body. As a reaction, the nihileth can reduce the damage it takes from a single source to 0. Radiant damage can be reduced only by half.

LEGENDARY ACTIONS

A nihileth may take three legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature’s turn. The nihileth regains spent legendary actions at the start of its turn.

• Detect. The aboleth makes a Wisdom (Perception) check.
• Tail Swipe. The aboleth makes one tail attack.
• Psychic Drain (costs 2 Actions). One creature charmed by the aboleth takes 10 (3d6) psychic damage, and the aboleth regains hit points equal to the damage the creature takes.

LAIR/LAIR ACTIONS

While aboleths create their lairs underwater, spending most of their time submerged, a nihileth lair can be encountered out of the water, often in a cave or a ruined, abandoned city.

On initiative count 20 (losing initiative ties), the nihileth can take a lair action to create one of the magical effects listed below. The nihileth cannot use the same effect two rounds in a row.

• Major Image: The nihileth casts major image (no components required) on any number of creatures it can see within 60 feet of it. While maintaining concentration on this effect, the nihileth can’t take other lair actions. If a target succeeds on the saving throw or if the effect ends for it, the target is immune to the nihileth’s major image lair action for the next 24 hours, although such a creature can choose to be affected.
• Grasping Waves: Pools of water within 90 feet of the nihileth surge outward in a grasping tide. Any creature on the ground within 20 feet of such a pool must succeed on a DC 14 Strength saving throw or be pulled up to 20 feet into the water and forced prone.
• Wave Blast: Water in the nihileth’s lair magically becomes a conduit for the creature’s rage. The nihileth can target any number of creatures it can see in such water within 90 feet of it. A target must succeed on a DC 14 Wisdom saving throw or take 7 (2d6) psychic damage.
• Leech the Dead: A nihileth can pull the lifeforce from those it has converted to nihilethic zombies to replenish its own life. This takes 21 (6d6) hit points from zombies within 30 feet of the nihileth, spread evenly among the zombies, and healing the nihileth. If a zombie reaches 0 hit points from this action, it perishes with no Undead Fortitude saving throw.

REGIONAL EFFECTS

The regional effects of a nihileth’s lair are as following:

• Underground surfaces within one mile of the nihileth’s lair are slimy and wet and are difficult terrain.
• As an action, the nihileth can create an illusory image of itself within one mile of the lair. The copy can appear at any location the nihileth has seen before or in any location a creature charmed by the nihileth can currently see. Once created, the image lasts for as long as the nihileth maintains concentration, as if concentrating on a spell. Although the image is intangible, it looks, sounds, and can move like the nihileth. The nihileth can sense, speak, and use telepathy from the image’s position as if present at that position. If the image takes any damage, it disappears.
• Water sources within one mile of a nihileth’s lair are not only supernaturally fouled but can spread the disease of the nihileth. A creature who drinks from such water must make a successful DC 14 Constitution check or become infected.