Demonic half brother of Merlin, they are both the sons of Belial. He was conjured by Merlin to protect Camelot in the days after the death of Arthur. When it was clear that the city was going to fall Merlin cast a spell to bond Etrigan with the mortal Jason Blood (in some accounts they are actually the same person). Blood was turned into an immortal but his constant struggles to keep Etrigan in check often resulted in him loosing his memory. Recently Blood has surfaced as an expert on the occult and for a time lived in Gotham City before he moved to Gateway City. Whenever Blood chants "Change, change, form of man, rise the demon Etrigan" he swaps places with/is transformed into, Etrigan.
Etrigan on the otherhand has become a much freer spirit and for a time a major power in Hell where he advanced to the level of a Rhyming Demon. Etrigan is an opportunist and will ally himself with almost anybody if he thinks that it will serve his purpose. He is a close friend of the bounty hunter Lobo, has served under the demon Neron and has even let the angel Zauriel live just because it would cause trouble for his own masters.