Armor Class 12
Hit Points 45 (6d10 + 12)
Speed 40 ft.
Damage Resistances bludgeoning, cold, piercing, slashing
Damage Immunities fire, poison
Condition Immunities charmed, frightened, grappled, paralyzed, petrified, poisoned, prone, restrained, stunned
Senses Darkvision 120 ft. (unimpeded by magical {@variantrule Darkness|XPHB}), passive Perception 11
Languages understands Infernal but can't speak
Challenge 3
Hellish Restoration. If the swarm dies in the Nine Hells, it revives with all its Hit Points in 1d10 days unless it is killed by a creature under the effects of a Bless spell or its remains are sprinkled with Holy Water.
Swarm. The swarm can occupy another creature's space and vice versa, and the swarm can move through an opening large enough for a Medium creature. The swarm can't regain Hit Points or gain Temporary Hit Points.
Multiattack. The swarm makes two Vile Slime attacks.
Vile Slime. m +4, reach 5 ft. Hit: 11 (2d8 + 2) Poison damage, or 9 (2d6 + 2) Poison damage if the swarm is Bloodied.
Monster Manual (2024), p. 194