Demonic one-eyed God of Death and evil King of the Fomorians, from Celtic mythology.
These were a race of gigantic warriors who liked nothing better than to invade somewhere, pillage it and then gloat horribly. Balor had one huge leg and, with his one evil eye, could kill someone just by peering at them. But he usually kept it closed to avoid tripping over dead bodies all the time. (From (From Godchecker.com)