The Blemmyes are part of Greco-Roman mythology, the names given to them meaning Headless Men. Chaosium first used them in 2009 for the Call of Cthulhu roleplaying game.
Background[]
The Blemmyes are children of Y'golonac, whom during the times of the Romans were found in the lands of Kush, Numidia, Egypt, and Africa Proconsularis. It's a nomadic race of warriors, that expanded the cult of Y'golonac and sacrificed those that resisted.
Behind the Mythos[]
Similar creatures named Bhlemphroims inhabit the planet Saturn in Clark Ashton Smith's Hyperborea story "The Door to Saturn".