Illithids, or Mind Flayers as they are commonly known, are the youngest of Asharra's children... and make up the bulk of her influence in the material plane. Powerful and aggressively expansionist, they have inhabited many parts of the underdark, lurking below the earth ready to move above and claim anything and anyone their mother demands. Illithid tend to gather under existing cities and towns, as their hunger forces them to prey on sentient races fairly often. Disappearances are common in places Illithids have moved to... though they take pains to hide themselves when abducting prey and do what they can to deflect the blame for them onto the restless dead plaguing the world.

Illithids are brilliant and dangerous in the extreme, as well as being powerful psions. Their mind powers can enslave even strong-minded foes or render others near catatonic under their psychic onslaught. Illithids use these powers to hunt for both food and slaves, and are very aggressive slavers... needing them for both food and labor. Slaves live hellish lives, and are bred forcibly to one another to provide more food for their Illithid masters. Most would choose suicide if they could.

A mind flayer is roughly comparable to a thin human in height and build, but the external resemblance stops at that point. An illithid’s head is a monstrous sight, resembling a fourtentacled octopus sitting atop the creature’s shoulders. The two eyes, uniformly pale white and without pupils, are sheltered beneath prominent brow ridges. The creature’s soft, moist skin is mauve in color and glistens beneath a thin coating of mucus. Mind flayers have three long, slender fingers and an opposable thumb on each hand, and two webbed toes on each foot. Each finger and toe is capped with a wicked-looking nail, which aren’t as dangerous as they seem. In fact, the nails are composed of soft cartilage and are mostly incapable of causing harm.

An illithid’s tentacles can vary from 2 to 4 feet in length when fully extended. When the creature is at rest and not excited, the tentacles appear shorter. Even then, they are in almost constant motion, writhing absentmindedly as the creature ponders. These limbs are extraordinarily dexterous and serve the mind flayer as an additional set of hands, even to the point of being used to punctuate or accentuate communication. The tentacle cluster surrounds a circular, jawless mouth ringed with rows of small, rasping teeth. The teeth serve primarily as tools for gripping and to prevent slippery gobs of brain matter from falling out of the mouth. An illithid does not bite through the skin and skull of a victim, instead dissolving it with a powerful enzyme transmitted through ducts in the tentacles. This enzyme acts so quickly that the tentacles appear to push right through the scalp and bone as if through soft clay. The enzyme is highly unstable and never survives more than brief contact with the air, making it impossible to harvest from slain illithids. No material other than illithid mucus is known to resist its corrosive effect.

From birth to death, the physiology of the illithid life cycle is unique, and unspeakably horrible. In basic configuration, a mind flayer is amphibious. The first portion of its life is spent as a tadpole hatched from an egg. An adult illithid spawns hermaphroditically two or three times during its lifetime, depositing about a thousand eggs in a briny pool constructed for just this purpose. The eggs hatch after about a month, releasing the writhing tadpoles into the pool. Illithids do not grow their own bodies. Instead, once a tadpole is mature it is is inserted into the ear, nostril, or eye of a helpless humanoid captive. Over a period of several days, the tadpole burrows into the host brain, consuming gray matter and gaining body mass in a nearly equal ratio. When the process is complete, the victim’s brain is completely replaced by the tadpole’s bloated tissue. The tadpole is neurologically melded onto what remains of the lower brain stem and assumes complete control of the body’s nervous system. The victim dies irrevocably, but the body lives on with the parasite serving as its brain.

Terrible devastation has been visited upon the illithids with the complete destruction of the underdark. Those few close enough to the Abyss to flee have done so, though how long they might survive in that tortured plane is unknown.