Cranium rats were psionically enhanced rats, transformed by mind flayers through bombardment with psionic energy.[1]


When isolated, cranium rats behaved like ordinary rats, using their telepathy to communicate basic feelings. When forming a swarm, however, the collective intelligence of the rats was combined into a single collective entity, which could also access enhanced psionic abilities from the mind flayer that created them. In such cases, a swarm of cranium rats could use psionic powers similar to spells.[1]


Cranium rats were used as spies for mind flayer colonies. They infiltrated surface communities and read the inhabitants' thoughts, later transmitting them to the elder brain.[1]



  1. 1.0 1.1 1.2 1.3 1.4 1.5 Wizards RPG Team (2016). Volo's Guide to Monsters. (Wizards of the Coast), p. 133. ISBN 978-0786966011.