Swarm of Intellect Devourers
Large swarm of Tiny aberrations, lawful evil
Armor Class 12
Hit Points 156 (24d10 + 24)
Speed 40 ft.
Abilities Str 13 (+1), Dex 14 (+2), Con 13 (+1), Int 19 (+4), Wis 14 (+2), Cha 14 (+2)
Skills Perception +10
Damage Resistances bludgeoning, piercing, slashing
Condition Immunities blinded, charmed, frightened, grappled, paralyzed, petrified, prone, restrained, stunned
Senses blindsight 60 ft. (blind beyond this radius), passive Perception 20
Languages understands Deep Speech but can’t speak, telepathy 60 ft.
Challenge 9 (5,000 XP)
Detect Sentience. The swarm can sense the presence and location of any creature within 300 feet of it that has an Intelligence of 3 or higher, regardless of interposing barriers, unless the creature is protected by a mind blank spell.
Swarm. The swarm can occupy another creature’s space and vice versa, and the swarm can move through an opening large enough for a Tiny intellect devourer. The swarm can’t regain hit points or gain temporary hit points.
Multiattack. The swarm makes two attacks with its claws and uses Devour Intellect.
Claws. Melee Weapon Attack: +6 to hit, reach 0 ft., one target in the same space as the swarm. Hit: 29 (6d8 + 2) slashing damage, or 15 (3d8 + 2) slashing damage if the swarm has half its hit points or fewer.
Devour Intellect. The swarm targets each creature it can see within 10 feet of it that has a brain. Each target must succeed on a DC 16 Intelligence saving throw against this magic or take 11 (2d10) psychic damage. Also on a failure, roll 3d6: If the total equals or exceeds the target’s Intelligence score, that score is reduced to 0. The target is stunned until it regains at least one point of Intelligence.
Body Thief. The swarm initiates an Intelligence contest with an incapacitated humanoid within 5 feet of it that isn’t protected by protection from evil and good. If it wins the contest, the swarm magically consumes the target’s brain and spawns an intellect devourer which then takes control of the body. While there, the intellect devourer has total cover against attacks and other effects originating outside its host. The intellect devourer retains its Intelligence, Wisdom, and Charisma scores, as well as its understanding of Deep Speech, its telepathy, and its traits. It otherwise adopts the target’s statistics. It knows everything the creature knew, including spells and languages.
If the host body dies, the intellect devourer must leave it. A protection from evil and good spell cast on teh body drives the intellect devourer out. The intellect devourer is also forced out if the target regains its devoured brain by means of a wish. By spending 5 feet of its movement, the intellect devourer can voluntarily leave the body, teleporting to the nearest unoccupied space within 5 feet of it. The body then dies, unless its brain is restored within 1 round.