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The Illithid, A study in terror

Illithids, known by many as Mind Flayers, have haunted the minds of players and DMs alike since 1975 when they first appeared in Gary Gygax’s Strategic Review newsletter. Since that time, they have appeared in every edition of D&D from OD&D to 5th edition, they have plagued hapless adventurers and have been the go to villain for many a DM. Join us as we delve into the terror that is the Illithid.


Illithids, or more commonly known as, Mind Flayers, are tall slender humanoids of roughly human shape. This is where their similarities to humans and other races of the realms ends. Their head is grotesque and octopus like with four and sometimes six ever moving tentacles where its mouth should be. The hands of an Illithid have three fingers and one thumb, slender and arthritic in appearance with bulging joints. The fingers end in long claw like nails. The feet of a Mind Flayer have but two toes that are webbed, a remnant of their amphibious past.

Their flesh is pale and mauve colored and slick with a glistening mucus. The eyes are pale white orbs that appear blind but are actually quite capable of sight. The eyes are set beneath a prominent brow ridge.


The internal anatomy of a Mind Flayer is similar to whatever their host species was. Mind Flayers have hearts, lungs, intestines, and all the usual internal organs in their recognizable locales. Mind Flayers do not reproduce in the same fashion that humans, elves, orcs, or any other humanoid species does. Rather they produce new Mind Flayers through a process called Ceremorphosis. This process relies on a host body.

The process of Ceremorphosis does however, alter the host body’s nervous system. The nervous system of an Illithid is more complex and advanced than that of any of the other humanoid races. Unlike you or I, the Illithid’s nervous system functions as a giant brain.

When a Mind Flayer consumes food, the digestive process differs from our own. When we consume food, it passes through our very simple digestive system where nutrients are extracted and sent throughout the body.

When a Mind Flayer consumes food, the food passes through what can best be described as a thinking, self-aware digestive system, scavenging enzymes and hormones and perhaps more importantly, the psychic energy of whatever was consumed. This has a great deal to do with the Mind Flayer being known for its consumption of the brains of its victims. Brains are not the only food that the Mind Flayer consumes though, Mind Flayer’s will consume other meats and fungi. Internal organs are a close second to a brain and are often preferred over other forms of food.

What is perhaps the most prominent physical feature on a Mind Flayer are the tentacles that surround its mouth. These tentacles could be anywhere from 2 to 4 feet in length and there are often times four of them, though in some Mind Flayers there could be up to six. When at rest or not excited the tentacles seem much shorter.

These tentacles are in almost constant motion, writhing as though they are snakes, independent of the Illithid’s body. The Illithid uses these tentacles as additional hands and are used in communication much in the same way that people not only speak with their voice but with her hands as well. These tentacles are known to be equally as strong as the rest of the Illithid, their grip being as powerful if not more so than the grip of the Illithid’s hands or arms.

The cluster of tentacles surrounds a mouth that is circular and without a jaw, much like a lamprey’s. Inside this mouth are rows of small teeth. These teeth are used to grab a hold of a victim. These teeth do not bite as teeth normally do; they merely secure the mouth to the skull. The tentacles drip a powerful corrosive solution that dissolves the scalp and the skull making it appear as though the tentacles are crushing the head of the victim when in fact the scalp and skull have been dissolved. The mouth is then free to slurp up the brain.

It is a particularly chilling sight to see a Mind Flayer devour the brain of its victim. The Mind Flayer will stun its opponent with a Psionic attack rendering them motionless but very much so aware of what is going on. The tentacles will wrap around the head drawing the head towards the mouth and the ring of circular teeth which penetrate the scalp and hold the head in place as the enzymes emitted from the tentacles begin to dissolve the scalp and skull of the victim, eventually causing it to cave in under the strength of the tentacles and pushing the brain into the awaiting mouth of the Mind Flayer.

It is no wonder why they are so widely feared that the mere mention of Illithid sends chills down the spine of even the bravest of adventurers.

The eyes of the Illithid are white milky orbs without a pupil suggesting a blindness since they live in dark places, subterranean caverns, holes and places that only the bravest or most foolhardy would dare venture. This is not the case however; they see quite well. The Mind Flayer sees in dark vision, up to 60 feet.

Their hearing is not as keen as that of a human or demi-human but it still serves them well. They can determine the direction a sound is coming in, though they have difficulty discerning certain portions of some sounds.


Illithid reproduction is equally as horrifying as their feeding habits. An Illithid is an amphibious life form, though its time spent in an aquatic environment is relatively short compared to the rest of its life cycle.

Illithids are hermaphroditic, adults will spawn approximately 2 to 3 times during their lifespan and will lay approximately a thousand eggs each time. These eggs will be laid in a murky pool specifically designed for the purpose of raising young. After about a month the eggs will hatch and will release what can best be described as a tadpole.

These tadpoles will spend approximately 10 years in this pool and are fed a vile mash of brain matter and internal organs. Throughout the 10 years that they spend in this pool they will be attended to by nursery attendants.

The tadpoles perform a dual function. They are both the newest generation of Mind Flayers and they are also food for the other occupants of the nursery pool, this occupant being the elder brain. The 10 years that the tadpoles live in this pool is akin to a vetting process, those that survive, not being devoured by the elder brain are deemed to be the fittest specimens the pool has to offer.

Mind Flayers do not grow their own bodies as we and other humanoids do. They are more akin to a parasitic infestation in a host body than anything else. Those tadpoles that are deemed to be the most fit are soon prepared for Ceremorphosis.

Ceremorphosis is the process by which a mature tadpole is introduced into the ear, nostril, or eye of a host body. Tragically, and savagely, these hosts are most often unwilling recipients of this process, held motionless and helpless by psionic ability of the Illithid. Once introduced into one of these locales, the tadpole will burrow into the host's brain, devouring the gray matter and growing in size. This is a process that usually takes several days. When complete, the hosts brain is completely gone and the tadpole is all that remains, thick and bloated, occupying the cavity of the host’ s skull much like their brain once did.

At this time the tadpole has effectively melded on a neurological level with what remains of the host's brain stem, taking complete control over the nervous system and the body. The host is dead, everything they once were, their thoughts, feelings, memories all gone but the body lives on. After about a week the process is complete and the parasitic tadpole is now the brain.

Reversing this process is nearly impossible.

Only certain races will be used by the Mind Flayers for Ceremorphosis. Humanoid mammals between 5 ½ feet and just over 6 feet are what is preferred. Humans, Elves, Drow and other such humanoids are eligible anyone smaller is not available to act as a host but rather will be relegated to the role of thrall (slave).

Once Ceremorphosis is complete nothing remains of the host, whatever race it was before the process is now unrecognizable. Instead, its tissues have all been replaced, the skin color is irreversibly changed in the facial features have given way to tentacles and great white orb like eyes. Hallmarks of the Mind Flayer.

We're not done exploring the Illithid, keep your eyes out for Part II.

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