The Lord of The Flies character might very well be one of the most famous religious figure in literature. Is there any being specifically that the creature was based on?
"Lord of the Flies" is a direct reference to Beelzebub (from the Hebrew ba'al z'vuv, בעל זבוב, literally "lord of flies.")
Beelzebub is well known as a dark god, a demon, or another name for Satan himself. The clear implication, in the context of the book, is that humanity -- freed of restraints, left to its own devices -- will naturally tend to cruel and hellish behavior; that people are devils, if given the chance.