Armor Class 12
Hit Points 45 (6d10 + 12)
Speed 40 ft.
Damage Resistances bludgeoning, cold, fire, lightning, piercing, slashing
Damage Immunities poison
Condition Immunities charmed, frightened, grappled, paralyzed, petrified, poisoned, prone, restrained, stunned
Senses Darkvision 60 ft., passive Perception 9
Languages Abyssal; telepathy 60 ft. (works only with creatures that understand Abyssal)
Challenge 4
Fetid Aura. con DC 12, any creature that starts its turn in a 10-foot Emanation originating from the swarm. The target has the Poisoned condition until the start of its next turn. While Poisoned, the target can take either an action or a Bonus Action on its turn, not both, and it can't take Reactions.
Swarm. The swarm can occupy another creature's space and vice versa, and the swarm can move through any opening large enough for a Small creature. The swarm can't regain Hit Points or gain Temporary Hit Points.
Multiattack. The swarm makes two Rend attacks.
Rend. m +4, reach 5 ft. Hit: 12 (3d6 + 2) Slashing damage, or 9 (3d4 + 2) Slashing damage if the swarm is Bloodied.
Monster Manual (2024), p. 104