Only humanoids weighing between 130 to 270 pounds (59 to 120 kilograms) and with heights between 5 feet and 4 inches to 6 feet and 2 inches (1.6 to 1.9 meters) were considered acceptable.
What about Brainstealer dragons? Mindwitness? Squidlings? Uchuulons? Urophions?
The creatures I have listed do not meet the criteria described, but are still considered Mind Flayers.
Not really. Those are classified as "Half-Illithids", or "Half-Mind Flayers".
A small variety of species could successfully undergo ceremorphosis, but if not from one of the fully compatible races, the result was called a "half-illithid", also known as a "ceremorph" or "flayer-kin". They do, however, still possess most of the powers of a regular Mind Flayer.
