Medium swarm of Tiny monstrosities, unaligned

Armor Class 15 (natural armor)
Hit Points 36 (8d8)
Speed 30 ft.

12 (+1) 11 (+0) 11 (+0) 5 (-3) 12 (+1) 5 (-3)

Damage Resistances bludgeoning, piercing, slashing
Condition Immunities charmed, frightened, grappled, paralyzed, petrified, prone, restrained, stunned
Senses passive Perception 11
Challenge 2 (450 XP)
Proficiency Bonus +2


  • 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.


The paving stones underfoot suddenly lurch and tumble over one another. Thousands of tiny limbs, pincers, and stingers break from the stony surface and frantically scuttle forward.

A cobbleswarm is made up of tiny, crablike creatures with smooth, stony shells. Individually they are referred to as cobbles. The creatures vary in size, shape, and color, but all have six segmented legs, a whiplike stinger, and a single eye.

Paving Stone Mimics. When the eye is closed and the limbs are pulled under the shell, cobbles are nearly indistinguishable from lifeless paving stones. Victims of cobbleswarms are caught unaware when the floor beneath them suddenly writhes and shifts, and dozens of eyes appear where there should be none.

Trap Affinity. Cobbleswarms have a rudimentary understanding of traps. They often hide in places where their Shift and Tumble ability can slide intruders into pits or across trapped areas. Kobold tribes prize them for this reason.

Section 15: Copyright Notice

Tome of Beasts 1 ©2023 Open Design LLC; Authors: Daniel Kahn, Jeff Lee, and Mike Welham.

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