Illithid, also known as "mind flayers", were a type of sadistic aberrations with powerful psionic abilities. In terms of height, weight, and build, they were roughly comparable to thin Humans, but it was at this point that any external comparison to humanoids ended. An illithid's flesh, was soft, supple, moist, and rubbery, resulting in an unmistakable texture easily distinguishable from any other creature by anyone familiar with it. Their skin ranged from mauve to greenish-violet in color, and their blood was silvery-white.
They had an innate talent for Telepathy and mind control, allowing them to dominate other beings. They often formed underground colonies led by an elder brain, which acted as the center of their collective consciousness. These colonies expanded their influence through infiltration and subjugation of other species. Illithid required a steady supply of sentient brains to survive, which they obtained through raids and manipulation. This need resulted in multiple attempts to subjugate and enslave entire species.
They relied on their mental abilities to control thralls and expand their domain. These thralls included various Mortalkind species that had been enslaved through psychic domination. The elder brain maintained absolute authority over its colony, ensuring that all members followed its will. Illithid rarely acted independently and relied on their shared knowledge to make decisions. This structure made them difficult to oppose, as they coordinated their actions with precision.
Illithid reproduction involved a parasitic process known as ceremorphosis. They placed a small larva into a host, where it gradually transformed the body into a new illithid. This method ensured the continuation of their species while eliminating the original identity of the host. Because of this process, they often abducted sentient beings to serve as hosts. Their reproduction method made them feared by many civilizations.
They primarily inhabited subterranean environments, avoiding the surface whenever possible. These underground cities were filled with tunnels and chambers designed to support their psionic society. They established strongholds in deep caverns and the Underdark, and sought to expand their influence through conquest and subterfuge. Some illithid sought to uncover ancient knowledge to increase their power. Their search for power often brought them into conflict with surface-dwelling civilizations.
Throughout history, illithid were known for their ruthless methods and their reliance on psionic abilities. Many civilizations attempted to resist their influence, but their mental powers made them formidable enemies. Some scholars speculated that they had once controlled vast empires before being driven underground. Despite numerous attempts to eliminate them, they always found ways to rebuild their numbers. Their continued existence posed a constant threat to free-thinking societies.