AC 13
HP 71 (11d8 + 22; bloodied 35)
Speed 0 ft., fly 40 ft. (hover), swim 40 ft.
Proficiency +2; Maneuver DC 13
Damage Resistances bludgeoning, piercing, slashing
Condition Immunities blinded, charmed, frightened,
grappled
, paralyzed, petrified, prone, restrained, stunned, unconscious
Senses darkvision 60 ft., passive Perception 10
Languages Deep Speech
Aberrant Physiology. The swarm doesn’t require air or sleep.
Swarm. The swarm can occupy another creature’s space and move through any opening large enough for a Tiny creature. It can’t gain hit points or temporary hit points.
Whispers of the Weird. The swarm murmurs and whispers constantly, speaking secrets in languages beyond mortal comprehension. A creature that starts its turn within 5 feet of the maw swarm and can hear it must make a DC 13 Wisdom saving throw or take 10 (3d6) psychic damage.
Bites. Melee Weapon Attack: +5 to hit, reach 0 ft., one target. Hit: 17 (4d6 + 3) piercing damage, or 10 (2d6 + 3) piercing damage if the swarm is bloodied .
When drowned humanoids sink to the depths of the sea, aboleths and other horrors find them. The transformations that are worked upon these bodies are too numerous to list and too awful to contemplate, but one form of them separates the maw and gullet from the corpse without ending its drive to consume. Aboleths lure maw swarms into areas they want to purge of all living matter, so that they can inhabit the area themselves.
Combat
The swarm moves into the space of the closest non-aberration and attacks it. It fights to the death.
Aboleths dwell beneath the Midnight Sea, but their minions explore every part of Underland.
CR 0–2 1 or 2 oculites ; 1d4 slitherwhites
CR 3–4 maw swarm ; 3 or 4 oculites
CR 5–10 aboleth champion
Treasure 150 iron coins (worth 10 gp each, but only to creatures that trade with aboleths); vicious longsword
CR 11–16 aboleth champion with 3 or 4 aboleth thralls , oculites , or slitherwhites ; aboleth brute with 1 or 2 aboleth thralls ; aboleth fallen ascendant
Treasure a barnacled mithral nameplate, torn from an ancient ship, bearing the name Red Queen (worth 5,000 gp), 10 vials of bubbling slime (each acts as a combined potion of greater healing and potion of water breathing )
Aberrations are unnatural beings that don’t belong to this plane of existence. Many aberrations are telepathic and use a mental power known as psionic power instead of magic. An aboleth is an aberration.