Illithid

In the Dungeons & Dragons game, Illithids (also known as mind flayers) are fictional humanoid beings with psychic powers that often live underground. They capture cave dwellers and other creatures living underground such as drow and dwarves, using them as slaves and as a food source. Mind flayers have four octopus-like tentacles around their beaklike mouths, and require the brains of sapient creatures as part of their diet. Mind flayers often possess magical abilities in addition to their psychic powers, and are often invunerable to illusion spells.

Mind flayers are also an important monster in Nethack and many other roguelike games. These games are mostly based on D&D, but use slightly different names and rules to avoid copyright problems. They were originally inspired by creatures from the Cthulhu Mythos.