Cranium Rats | Monster Guide for D&D

Mind flayers create cranium rats by bombarding rats with psionic energy. Cranium rats are some what smarter than ordinary rats and behave as such. If enough cranium rats come together to form a swarm, they merge their minds into a single intelligence with the accumulated memories of all the swarm’s constituents. The rats become smarter as a result, and retain their heightened intelligence for as long as the swarm persists. The swarm also awakens latent psionic abilities implanted within each cranium rat by its mind flayer creators, bestowing upon the swarm psionic powers.

Tiny Aberration, Unaligned

Armor Class: 12
Hit Points: 2 (1d4)
Speed: 30 ft.

    STR – 2 (-4)
    DEX – 14 (+2)
    CON – 10 (+0)
    INT – 4 (-3)
    WIS – 11 (+0)
    CHA – 8 (-1)

Senses: darkvision 30 ft., passive Perception 10

Languages: telepathy 30 ft.

Challenge: 0 (10 XP)

Proficiency Bonus: +2

Telepathic Shroud. The cranium rat is immune to any effect that would sense its emotions or read its thoughts, as well as to all divination spells.


Bite. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 1 piercing damage.


Illumination. The cranium rat sheds dim light from its exposed brain in a 5-foot radius or extinguishes the light.