Ceremorphosis is the natural reproduction process of the mind flayer. It involves inserting a live illithid tadpole into the mind of a captive humanoid host, consuming their mind over the course of days and transforming the body into a mind flayer.
The word "ceremorphosis" derives from a language called the Elder Tongue, with cere meaning "brain", and morphe meaning "form".
The mind flayer is an amphibious species, and its life cycle begins as a tadpole hatched from a clutch of tiny eggs.
An adult mind flayer spawns around 1,000 tiny eggs, which it deposits in a spawning pool located in the center of a mind flayer city. A mind flayer will only produce spawn in this manner only two or three times in its lifetime.
The eggs hatch after one month, and begin a ten-year process of growth, during which they are fed a diet of carefully prepared brain slurry by the mind flayer community.
Only one tadpole in a thousand survives to maturity, with most consumed by the elder brain who inhabits the central pool. A fully-grown tadpole is three inches long and resembles an octopus with four tentacles forming its tail.
The mature tadpole is inserted into the ear of a living humanoid, where it burrows into the creature's brain. It quickly consumes the brain and grows to fill the creature's skull, leaving the lower brain stem intact. The tadpole attaches itself to the brain stem, melding its mind with the creature's body. Implantation is complete within only three minutes.
Over the next few days, the body undergoes a massive physical transformation into the recognizable form of a mind flayer. All traces of the original creature's mind are erased by the process. The process of ceremorphosis is irreversable even by magical means after one hour.
The transformation into a mind flayer is complete after seven days. Following ceremorphosis, a mind flayer takes up to 21 years to reach full maturity.
The process typically takes place in birthing pods, special round chambers for the purpose. The host is strapped to a table to prevent injury to the body. The host will also be struck with with a psionic blast, in order to render it docile.
Mind flayers are highly selective when choosing hosts for ceremorphosis. The process is highly sensitive to factors such as height, weight, species and even brain chemistry, and only the healthiest captives are chosen.
Successful hosts are almost always mammalian humanoid species of approximately the height of an adult human. Common victims of ceremorphosis include humans, elves, githzerai, githyanki, and grimlocks. The optimum physical range is between 130 and 270 pounds in weight, and between 5'4" and 6'2" in height.
An illithid selecting a creature too large or small, such as an ogre or halfling, will fail to develop at the correct rate. This inevitably results in the death of both the illithid tadpole and the host. Attempts to implant dwarves have failed.
Experimental hosts are occasionally chosen, which almost always result in failure. Rare successes include the urophion, created by the implantation of an illithid tadpole into a roper; the mindwitness, from a beholder, the tzakandi, from lizardmen; and mozgriken, from svirfneblin. Such unusual forms are sometimes called ceremorphs, or flayer-kin.
Adult mind flayers themselves are physiologically incapable of being subject to ceremorphosis.
Retained host memories
On occasion, a small fragment of the original host's memory survives the ceremorphosis process. This condition is known as "partialism", and mind flayers who become aware of the existence of the memory fragment often attempt to remove it by any means necessary.
A herbal concoction called laethen allows an individual to retain their identity and memories in the event that they are subjected to transformation into a mind flayer. A single dose lasts one week, but only effective in 40% of cases.
Failure to implant
A mature illithid tadpole which is not implanted will continue to grow and develop until it is too big to be implanted. Failure to implant a mature tadpole is taboo among mind flayers, and they will intentionally destroy such creatures.
A tadpole which somehow avoids destruction and develops to the size of around two feet in length is sometimes referred to as a larval flayer. It uses its four tentacles to slowly consume brains.
When a mind flayer city is destroyed or abandoned, hundreds of surviving illithid tadpoles may reach maturity without being implanted into a host or consumed by an elder brain. Without a food supply, the tadpoles must adapt or perish.
In some cases, the tadpoles survive by violently cannibalizing their fellow spawn until a single massive tadpole is the only survivor. It scours the Underdark, consuming brains of small animals and growing larger until it can finally consume a humanoid brains, at which point it attains a primitive sort of ceremorphosis. Such a terrifying creature is known as a neothelid, and they can grow to truly gargantuan proportions.
In at least one instance, following the fall of a mind flayer empire, a group of tadpoles survived by escaping the breeding pool and wandering the caverns together en masse. These creatures, called illithocytes, evolved the ability to reproduce by budding. They reach up to four feet in size, and travel together in a a psionically coordinated group. Illithocytes are a major source of food for the larger neothelids.
AD&D 2nd edition
The first known reference to the process of ceremorphosis appears in The Illithiad (1998), one of the lore-heavy books published in late AD&D 2nd edition. Pages 10-14 describe the mind flayer life cycle in detail.
Ceremorphosis by mind flayers of the Forgotten Realms are described in Drizzt Do'Urden's Guide to the Underdark (1999), p.21-23,43,76-78,81,102,121.
D&D 3rd edition
Ceremorphosis and the illithid life cycle are described in Lords of Madness (2005), which dedicates a chapter to the mind flayer. The process is also mentioned in the article Monsters of the Mind: Minions of the Mind Flayers, Dragon #337 (Nov 2005).
D&D 4th edition
Ceremorphosis is briefly described in Menzoberranzan (4e) (2012), p.114.
D&D 5th edition
Reception and influence
Ceremorphosis is depicted in Baldur's Gate III, in which both the player character and the githyanki fighter Lae'zel are among a group of people infected with mind flayer tadpoles aboard a Nautiloid spelljamming ship.
- The Illithiad (1998), p.10-14.
- Menzoberranzan (4e) (2012), p.114.
- Volo's Guide to Monsters (2016), p.72.
- Drizzt Do'Urden's Guide to the Underdark (1999), p.102.
- Volo's Guide to Monsters (2016), p.176.
- The New Illithid Arsenal, Dragon #255 (Jan 1999), p.33.
- Drizzt Do'Urden's Guide to the Underdark (1999), p.22.
- Dawn of the Overmind (1998), p.56.
- Complete Psionic (2006), p.133.
- Expanded Psionics Preview #4: Psionic Monsters, Dragon #318 (Apr 2004), p.90-92.