The fall of Lucifer

Two traditional prooftexts for the fall of Lucifer are Isa 14 and Ezk 28. Although Isa 14 isn't directly about the fall of Lucifer, it employs civil war in heaven imagery. The losers are expelled. The interpretation of Ezk 28 is complicated by ambiguous syntax. A neglected passage is Isa 24:21-22, which suggests disobedient angels. 

The clearest OT passage might be Dan 10. It has four figures, three of whom seem to be angelic. There's Daniel. Then there's a good angel, who might be Gabriel or a cherub (see Iain Duguid's commentary, 180-81). The good angel is blocked by "the Prince of Persia," who appears to be an evil territorial spirit. The Prince of Persia is then overpowered by the Archangel Michael. The fact that the Prince of Persia has the ability to obstruct the good angel suggests that some fallen angels are more powerful than some heavenly angels. 

Although this doesn't narrate the fall of angels, it seems to presume their downfall. There are only two logical options: either they were originally evil or else they became evil. 

This also raises the intriguing question of where the Prince of Persian ranks in the infernal chain-of-command. As a territorial spirit, we might consider him to be a Satanic subordinate–if we think Satan has a wider sphere of influence than a territorial spirit. 

On the other hand, Satan is a finite agent. He must concentrate his efforts. At the time, Israel was in exile. And ancient Israel was the locus of God's earthly kingdom. So perhaps the Prince of Persia is Satan himself. At that time and place, Israel was the primary thing for Satan to oppose. And the base of operations temporarily shifted to the exilic community. In terms of diabolical strategy and allocation of resources, it makes sense for Satan to direct his efforts at the exilic community. 

Admittedly, this is somewhat speculative. There's not a lot to go on. At a minimum, the passage is an indirect witness to the angelic fall. But the angelic villain in this passage may well be Satan himself. That would dovetail with other altercations between Satan and the Archangel Michael (Jude 9; Rev 12:7-9).