Cranium rat

Cranium rats were psionically enhanced rats, transformed by mind flayers through bombardment with psionic energy. They were interspersed through a normal rat population of a city to be used as spies by Illithids.

Description
Cranium Rats were indistinguishable from regular variants of their respective species save for their enlarged and exposed brains. It was possible for these brains to exude light.

Behavior
When isolated, cranium rats behaved like ordinary rats, using their telepathy to communicate basic feelings like hunger and fear. Even in this state they were still significantly more intelligent than normal vermin. When forming a swarm, however, the collective intelligence of the rats was combined into a single entity. The more Cranium Rats in a swarm the more intelligent the swarm would become, with an average sized swarm of rats holding an unnerving level of intelligence. Cranium Rat Swarms spoke in the collective, using 'Us' and 'we' as opposed to 'I' or 'Me'. Rats separated from the swarm do not suffer an immediate intelligence drop, but rather gradually lose their minds over a course of several days, although they do lose access to their psychic powers. This loss is immediately undone when they swarm again. While dangerous entities they are not normally violent unless ordered to attack, sticking to reconnaissance.

Abilities
Alone Cranium Rats were weak and cowardly, with no more offensive ability than an ordinary rodent. They were able to generate light using whatever weak psionic powers they possessed, and were immune to having their minds read.

When in a swarm however Cranium Rats could also access enhanced psionic abilities similar to spells. , implanted by their Illithid masters. So long as enough Cranium Rats existed in a single area (approximately 30) they could wield these abilities to achieve a variety of affects. Cranium Rat Swarms could use these abilities to attempt to read the minds of their targets, or decipher writing and spoken word. They could also attempt to control the minds of targets at will, although such a method was limited to simple orders. With more effort they could try to mentally dominate their enemies for up to an hour or scramble their minds, although both of these were strenuous enough that they took a day to recharge. The collective gained when the rats combine was intelligent enough to cut off members from the hive who had been mentally controlled. If their mental powers proved ineffective they were also capable of simply swarming their targets like regular rats.

Cranium Rats do not conduct direct attacks, but will ambush an opponent when they are walking somewhere or asleep. If they cannot kill a target quickly they will scatter, splitting their intelligence and making the entity responsible practically impossible to capture. They will also do so if under attack, rather than fight back.

Society
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. Discovery of their operations was met with swift death, so as to continue unhindered. If a few rats escaped the range of the Elder Brain's connection, it and its servants were unconcerned as new ones could be created on the fly.

Ecology
Cranium Rat biology was similar to normal rat biology, although they ate a greater amount of meat. It is unknown if reproduction creates regular or Cranium Rats. For one reason or another Cranium Rats did not gather into groups too dense. It is possibly because such a group would ascend to a higher level of being, or that such overpopulation is inefficient to accomplish anything.