Medium Swarm, Unaligned
Armor Class 15 (natural armor)
Hit Points 36 (8d8)
Speed walk +30
Challenge 2
Damage Vulnerabilities False
Damage Resistances bludgeoning, piercing, slashing
Damage Immunities False
Condition Immunities charmed, frightened, grappled, paralyzed, petrified, prone, restrained, stunned
Senses passive Perception 11
Languages —
False Appearance. While the cobbleswarm remains motionless, it is indistinguishable from normal stones.
Shifting Floor. Whenever the cobbleswarm moves into a creature's space or starts its turn in another creature's space, the creature must succeed on a DC 13 Dexterity saving throw or fall prone. A prone creature must succeed on a DC 13 Dexterity (Acrobatics) check to stand up in a space occupied by the swarm.
Swarm. The cobbleswarm can occupy another creature's space and vice versa, and the swarm can move through any opening large enough for a Tiny stone. The swarm can't regain hp or gain temporary hp.
Stings. Melee Weapon Attack: +3 to hit, reach 0 ft., one target in the swarm's space. Hit: 15 (6d4) piercing damage, or 7 (3d4) piercing damage if the swarm has half its hp or fewer.
Shift and Tumble. The cobbleswarm pushes a prone creature in its space up to 5 feet away from it.
Source: Tome of Beasts 2023 · OGL/Open