Christianity presents the Devil, aka Satan or Lucifer, as a fallen angel, the Prince of Light, who was cast out of Heaven following an attempt to overthrow God and assume control of Heaven. Most Evangelicals and other Christian conservatives describe the Devil as an actual entity who is able to tempt mankind to sin, possess the minds and bodies of humans, and inflict physical and mental sickness. He rules over Hell and has legions of other demonic fallen angels to serve him in his works, including the eternal torment of sinners who have been condemned to his domain. This entire concept is purely and exclusively New Testament and has no factual basis in any of the Old Testament scriptures. Christians constructed the Devil from myths which the Jews themselves had borrowed from the Babylonians, Philistines and Canaanites, adding a few vague references in the Old Testament to assign names and add substance to their creation. Just a few of the many demonic figures which were combined to create Christian Devil:
1) Beelzebub, (Baal-zebub, Lord of the Flies, derived from the Hebrew 'Baal-Zevuv' in the given text) actually was one of the many Baals (Lords or Masters) worshipped by the Philistines and Canaanites. Beelzebub is a corruption of the name Baal-Zebul, which translates 'Prince Baal.'  He was the god of the Philistine city Ekron, and is mentioned in the OT at 2 Kings 1:2-16, where God condemns Ahaziah for consulting with the god of the Philistines rather than with himself, God of the Jews. The OT makes no mention of anything demonic about Baal-Zebub, just Ahaziah's sin of consulting with a Philistine god rather than with his own Jewish god. Some translations of the New Testament have Beelzebub tempting Jesus, but many other NT translations have substituted Satan, the Devil or Lucifer as the tempter in that story.

2) Asmodeus, who was considered as the prince of revengeful demons. Hebrew myth identifies him as the eldest son of the mother of all demons, Lilith (more on her later).

3) Abaddon, aka Apollyon the Destroyer, ruled in Sheol, the Pit, Hell, which was not a place of punishment or reward but merely a place inhabited by all the dead, the Hebrew equivalent of the GrecoRoman versions of the Underworld.

4) Satan and Lucifer, references to both of whom are combined to create one Devil with two names. These are completely covered further down in this site.

Not a single one of the OT demons ruled over Hell as it is described by Christians or had any power to punish people after death. They could inhabit the bodies of people and do them physical harm or even cause their bodies to act sinfully during the course of the possession, but they had no power to tempt or seduce humans to sin resulting in their eternal damnation. They were merely demonic entities many - but not all - of whom descended from Adam's first wife Lilith as described in Hebrew Midrash, and/or were borrowed from other popular religions of that time.
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