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, paralyzed, petrified, prone, stunned
Senses passive Perception 11
Challenge 2 (450 XP)

Special Traits

  • False Appearance. While the swarm remains motionless, it is indistinguishable from normal stones.
  • Shift and Tumble. As a bonus action, the swarm can push a prone creature whose space it occupies 5 feet.
  • Shifting Floor. Whenever the swarm moves into a creature’s space or starts its turn in another creature’s space, that other creature must make a successful DC 13 Dexterity saving throw or fall prone. A prone creature must make a successful DC 13 Dexterity (Acrobatics) check to stand up in a space occupied by the swarm.
  • Swarm. The swarm 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 hit points or gain temporary hit points.


  • Stings. Melee Weapon Attack: +3 to hit, reach 0 ft., one target in the swarm’s space. Hit: 10 (4d4) piercing damage, or 5 (2d4) piercing damage if the swarm has half its hit points or fewer.


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, and kobold tribes prize them highly for this reason.

Section 15: Copyright Notice

Tome of Beasts. Copyright 2016, Open Design; Authors Chris Harris, Dan Dillon, Rodrigo Garcia Carmona, and Wolfgang Baur.