"My name is Legion: for we are many.”
Legion was a biblical demon or a collection of demons first encountered in Mark 5:9 of the New Testament. Legion was the group of demons possessing a man from Gadarenes, and whom were subsequently cast out of the man and into a herd of pigs. Those pigs then drowned themselves in the sea of Galilee.
This story has spawned many references and allusions in popular culture. Television shows have used the idea of multiple possessions or personalities as a plot device, even going so far as to name the character Legion or to reference the famous quote. Shows like Angel and Supernatural specifically depict demons who claim to be the actual Demon Legion. Even Gargoyles referenced it in an episode titled Legion. Legion is even a movie based completely on the character concept from the bible and transformed into a modern day graphic novel-esque movie