Illithid

Illithids (commonly referred to as mind flayers) are a race of evil aberrations from Dungeons & Dragons. They generally reside in the Underdark where they forever scheme and plot against other races that they deem "inferior". Illithids consider themselves to be above other forms of life and seek power and dominance over all they survey.

Appearance
Illithids are humanoid in basic shape - one head, two arms and two legs - but the similarities with humans end there. Their physical appearance is what other races would call nightmarish: their heads are bulbous and pulsating with a pair of sunken eyes and four writhing tentacles surrounding a hideous maw. Their skin tones range from a deathly white to varying shades of blue, purple or even green. Their fingernails grow into long, wickedly sharp claws. Illithids generally prefer to dress in dark, regal-looking attire such as long, flowing robes and cloaks.

Biology
Illithids are hermaphroditic creatures who each spawn a mass of larvae two or three times in their life. The larvae resemble miniature illithid heads or four-tentacled tadpoles. Larvae are left to develop in the pool of the Elder Brain. The ones that survive after 10 years are inserted into the brain of a sapient creature. Hosts are determined in a very specific manner. Hosts generally are humanoid creatures that are between 5'4" and 6'2". The most desirable of races for hosts are Human, Drow, Elves, Githzerai, Githyanki, Grimlock, Gnolls, Goblinoids, and Orcs. Upon being implanted, the larva then grows and consumes the host's brain, absorbing the host's physical form entirely and becoming sapient itself, a physically mature (but mentally young) illithid. This process is called ceremorphosis. Illithids often experiment with non-humanoid hosts, but ceremorphosis involving other creatures usually fails, killing both host and larva.

When an illithid undergoes ceremorphosis, it can occasionally take on some elements of the absorbed host creature's former mind, such as mannerisms. This typically manifests as a minor personality feature, such as a nervous habit and/or reaction (e.g., nail-biting or tapping one's foot), although the process that determines the type and number of traits so inherited appears to be stochastic. An adult illithid has even been known to hum a tune that its host knew in life. Usually, when a mind flayer inherits a trait like this, it keeps it a closely guarded secret, because, were its peers to learn of it, the illithid in question would most likely be killed. This is due to an illithid legend of a being called the Adversary. The legend holds that, eventually, an illithid larva that undergoes ceremorphosis will take on the host's personality and memory in its entirety. This "Adversary" would, mind and soul, still be the host, but with all the inherent abilities of an illithid. Occasionally, ceremorphosis can partially fail. Sometimes the larva does not contain enough chemicals to complete the process, sometimes there is psionic interference. Whatever the reason, it has happened that ceremorphosis has ended after the internal restructuring, resulting in a human body with an illithid's brain, personality and digestive tract. These unfortunates must still consume brains, typically by cutting open heads (as they lack the requisite tentacles). These beings are often used as spies, where they easily blend in with their respective host types.

The illithid society also maintains a long-standing taboo related to deviations to or failures of the ceremorphosis process and hunt and destroy such exceptions. Occasionally, mind flayer communities are attacked (often by vengeful githyanki and githzerai) and their inhabitants must flee. This leaves the larvae unattended. Bereft of exterior nourishment, they begin to consume one another. The survivor will eventually leave the pool in search of food (i.e., brains). If the larva consumes the brain of an intelligent creature, it will take over the body and form into a fully grown illithid. In Complete Psionic, it was revealed that illithids have a step between larva and neothelid called a Larval Flayer, which looks like an overgrown tadpole. The existence of these beasts is a guarded secret among illithids, and it is considered impolite to speak of them.

Society
An illithid city is ruled by a creature called an Elder Brain which lives in a pool of cerebral fluid in the city's center. When an illithid dies, its brain is extracted and taken to the pool. Illithids believe that when they die, their personality is incorporated into the Elder Brain, but this is not the case. When the brain of an illithid is added to the Elder Brain, the memories, thoughts, and experiences are consumed and added to the sum of the whole, but all else is lost. This fact is a closely guarded secret of the Elder Brains, since all illithid aspire to a form of immortality through this merging process. An extremely ancient Elder Brain is called a God-Brain because its psionic powers are almost limitless.

Since the Elder Brain contains the essence of every illithid that died in its community, it functions in part as a vast library of knowledge that a mind flayer can call upon with a simple telepathic call. The Elder Brain in turn can communicate telepathically with anyone in its community, issuing orders and ensuring everyone conforms.

Illithids generally frown upon magic, preferring their natural psionic ability. Psionic potential is an integral part of the illithid identity, and the Elder Brain cannot absorb the magical powers of an illithid mage when it dies. They tolerate a limited study of wizardry, if only to better understand the powers employed by their enemies. However, an illithid who goes too far and neglects his psionic development in favor of wizardry risks becoming an outcast. Denied the possibility of ever merging with the Elder Brain, such outcasts often seek their own immortality through undeath, becoming alhoons.

Illithids typically communicate through psychic means. They project thoughts and feelings to each other in a way non-illithids can scarcely comprehend. When they do feel the need to write, they do so in "qualith." Instead of typical alphabet-based writing, illithids write in qualith by making marks consisting of four broken lines. They use each tentacle to feel the breaks in the lines, making it basically similar to braille. However, qualith is extremely complex, as each line modifies the preceding lines through explaining abstract concepts associated with the above words in ways no human can understand; only by understanding all four lines simultaneously can the meaning be understood properly.

Religion
Traditionally illithids revere a perverse deity named Ilsensine. In 2nd edition, they have a second deity named Maanzecorian, who is later killed by Orcus in the Planescape adventure module Dead Gods. Although Ilsensine is the illithid patron deity, few mind flayers actively worship him, thinking themselves the most powerful creatures in the universe.

Variants
There are numerous illithid types which are listed below.
 * Elder Brain
 * Neothilid
 * Larval Flayer
 * Alhoon
 * Ulitharid
 * Vampiric Illithid
 * Yaggol
 * Brainstealer Dragon
 * Illithocyte
 * Kezreth
 * Mindwitness
 * Mozgriken
 * Nerve Swimmer
 * Tzakandi
 * Uchuulon
 * Urophion

Abilities
Common illithid abilities include:-
 * Mind Blast - A burst of psychic energy that inflicts great pain upon a victim.
 * Extract - Illithids use their mouth tentacles to rip the brains out of their victims' skulls and devour them.
 * Charm Monster - Illithids can exert mental control of any monster within a range of 60 feet.
 * Detect Thoughts - Illithid telepathy allows them to read the minds of their enemies.
 * Suggestion - An illithid can issue a mental command to compel a victim to carry out its will.

Trivia

 * Gary Gygax, creator of Dungeons & Dragons, had stated that his inspiration for mind flayers came from Cthulhu and the works of H.P. Lovecraft.