The Crown of the Stars - A Spelljammer 5e Tale
However and whenever it occurred, when the illithids arrived in the wild space of the far past, they immediately began to build an empire by enslaving many sentient creatures. They were very successful, and soon their worlds-spanning empire became the largest one the multiverse had ever seen. They had the power — in terms of psychic potency and the manpower of countless slaves — to fashion artificial worlds. One such world was this empire’s capital, called Penumbra, a diskworld built around a star, which was a thousand years in the making. Such was their might that the Blood War paused as the demons and devils considered a truce to deal with the illithid empire.
Eventually, the primary slave race of the illithids developed resistance to the mental powers of their masters, and revolted. Led by the warrior Gith, the rebellion spread to all the illithids’ worlds, and the empire collapsed. The illithid race itself seemed doomed.
Fortunately for the illithids, Gith was betrayed by one of her own generals, Zerthimon, who believed she had grown tyrannical and over-aggressive. Civil war erupted, and the race factionalised into the pirates of Gith and the twilight monks. This disruption allowed the illithids to retreat to underground strongholds where they still dwell.
Since then they have dreamed about rebuilding their empire and will do anything to accomplish it.
Typical physical characteristics
Illithids have a humanoid body with an octopus-like head. They have four tentacles around a lamprey-like mouth, and require the brains of sentient creatures as part of their diet. An illithid who snares a living creature in all four of its tentacles can extract and devour its living brain. Their eyes are pale white, and they can see perfectly well in both darkness and light. Their sense of hearing is slightly poorer than a human’s; they have difficulty distinguishing between several sounds mixed together, yet they are good at discerning from what direction sounds came from. Their skin is purplish blue to gray-green and covered in mucus, and is very sensitive to sunlight. They loathe sunlight, though it does not actually harm them.
One of their most feared powers is the dreaded Mind Blast, where the illithid emits a cone-shaped psionic shock wave with its mind in order to incapacitate any creature for a short amount of time. Illithids also have other psionic powers, generally telepathic in nature, although their exact effects have varied over editions. Other powers include a defensive psionic shield and powers of psionic domination for controlling the minds of others.
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 feet 4 inches and 6 feet 2 inches. The most desirable of races for hosts are Human, Drow, Elves, Githzerai, Githyanki, Grimlock, Gnoll, Goblinoid, and Orc. 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). This unmorphed larvae is known as a Neothelid. If the neothelid consumes an intelligent creature it will awaken to sapience and psionic abilities and grow to immense size, while retaining its memories of savage survival.
Currently, the illithids are in a period of intense study and experimentation, gathering knowledge of all sorts that will enable them to eventually reconquer the universe and hold it for good. They frequently meddle in the politics of other races through subtle psychic manipulation of key figures, not to cause chaos but so as to better understand the dynamics of civilization. They regularly probe the minds of surface dwellers so as to gather intelligence and learn about new advances in magic and technology. They also do a good deal of research themselves, mainly focused on developing new psychic powers.
Illithids regularly conduct raids on all sentient settlements to acquire new thralls, because their existing stock of sentient thralls do not breed fast enough to satisfy their food and labor needs. Typically, a group of mind flayers will teleport to the settlement and swiftly incapacitate them with their psychic powers. The captives will then be marched all the way to the illithids’ underground settlement by specially trained and conditioned thralls. Great care is taken to cover their tracks.