The Illithid came for Rellan today.
They stood in the entrance of the holding cell like wet, bruise-purple statues draped in funerary black. They were motionless save for the subtle, vermiform writhing of their tentacles, and the pulsing of the thick veins wreathing their bulbous skulls.
They had been taking us one by one from the holding cell, for whatever obscure need they had. I say need--though the very concept seems incongruous with the cold dispassion which characterized their actions. Their intelligence was apparent in their black eyes, but inhuman in its workings, and far beyond ours, and so unknowable.
The psychic buzzing that always accompanied their presence seemed to paralyze us at their will. Faintly, sometimes in these visits I thought I could hear their telepathic voices, like distant whispers, as they discussed among themselves which of us to select. These psychic vibrations I perceived as pitched something like the voices of old women, but alien in their lack of inflection or emotion.
Today, the deliberations were quick. The buzzing rose in volume, and Rellan was seized by the emanations of their mind and walked stiffly into the presence of our captors, face contorted with the agony of his futile resistance. In a moment, they were gone, and we were free from the effects of their overbearing psychic presence.
As with the others taken before, we never saw Rellan again.
- From a journal found in a cleared room in the Labyrinth of Ulthraun, delivered to Tuvo brek Amblesh, Magister of the Library of Tharkad-Keln.
One of the most appealing things about the Mind Flayers is their inherent alien and mysterious nature. Multiple origins have been given for them in various D&D products over the years and editions. These different origins are often irreconcilable, at least in part.
I see that as a design feature rather than a bug. Mysterious and compelling adversaries deserve equally murky and evocative origins.
In that spirit, here are four possible origins for the Mind Flayers. They're in no way completely "original" and that's purposeful. They draw from a host of pulp, weird, and science fiction sources, as well as referencing, in some ways, origins offered in official source material. They also utilize modern terminology to help evoke a pseudo-scientific air, but also to help the modern reader come at these classic creatures in a new way. They're are not necessarily intended to be used verbatim "in game." On the other hand, a dying astronaut whispering his last words, or an ancient, half-malfunctioning video screen relaying one of these origins would be just the sort of genre-bashing that classic D&D was built from...
- The Mind Flayers are abhuman mutants from a far future, dying earth. Endeavoring to save their civilization from extinction, they have been using all their failing super-science to cast as many of their dwindling number as they can back through the eons. In the current era, they are interested in humans as food--and as subjects for experimentation. They hope to force-evolve mankind into their species, and restore a breeding population of their once mighty race.
- The Illithids are vampiric thoughtforms from a higher plane. If they can be glimpsed in their "true" form by magical or psionic means, they resemble translucent, glowing jellyfish. They descended into material forms out of hunger and curiosity millennia ago, drawn like moths to a flame by the psychic energy of nascent sentient life.
- The Mind Flayers hail from a planet destroyed by the gods themselves--either as punishment for their impious presumption, or out of fear of their developing power. Some illithid escaped the death of their world, and hide in subterranean enclaves, bidding their time, and planning their vengeance.
- The Illithid are but the drones or puppets of ancient aquatic, elder brains. Either these coral-like beings evolved here, or perhaps arrived from some alien world. Whatever their origins, they construct larva which infect intelligent hosts and transform them biologically into illithid, subsuming them in a group mind. The ultimate goals of these elder brains are unknown.