Redemption For Fallen Angels

The Bible might not mention fallen angels being offered salvation or any of them being restored to Yahweh's side, but it is absolutely possible for a deity that wants everyone to be saved (2 Peter 3:9) to have that same desire for the redemption of rebellious angels, which would also to some extent bear the "image" of God.  By having consciousness with an intellect (though demons would have to either make assumptions or ignore reason and thus would knowingly disregard it in order to oppose Yahweh), a will, and moral responsibility, angels would share at least many qualities of humans that are likely what Genesis means when it says humans have God's image (1:26-27).  Out of all the somewhat sparse details the Bible actually reveals about angels serving God or that serve Satan, nothing is included that would contradict the redemption of fallen angels.

Demons are at first introduced as malevolent spirits that oppose Yahweh, with Genesis, the rest of the Torah, and much of the Old Testament not focusing on them despite the occasional reference--not even "the devil, or Satan" (Revelation 12:9), has his origins or his betrayal of Yahweh detailed until Ezekiel 28, and that is if the fallen cherub mentioned there really is Satan.  Genesis does not so much as specify that the serpent in Eden was Satan (the aforementioned verse in Revelation 12 touches upon that at the end of the Bible).  A great deal of what many people believe or are told about Christian demonology is unrelated to what the Bible says about the matter, or it is assumed on the basis of hearsay (a kind of pathetic epistemological faith).  Some insist that demons are excluded from salvation because they are not human, yet this is not a Biblical teaching.

Perhaps, if Christianity is true (as seems to be the case), demons can be saved, and perhaps not.  Either option is logically possible and its alternative could have been the case instead, since whether angels are redeemed is ultimately about God's willingness to offer redemption to them and either of these responses to evil spirits does not conflict with logical axioms.  All that the Bible says to address the fate of general demons is that hell was created for them (Matthew 25:41), that there will be torment when justice is imposed on them (Matthew 8:29), and that some of them are already confined in "Tartarus" as they await their eventual judgment (2 Peter 2:4).  Of Satan specifically, Revelation 20:10 says he will be placed in the lake of fire and suffer eternally, though Ezekiel 28:18-19, if the devil is the demon being spoken of, very plainly states that he will actually at some point be reduced to nonexistence as other verses promise for unrepentant humans.  Matthew 10:28 is one place emphasizing that for humans, justice is their annihilation, and Revelation 20:10 might in part be a very figurative exaggeration.

The Biblical fate of demons being hell is fairly obvious.  It is clear from reason and from the lack of exclusivity with what the Bible does say that their punishment in hell might potentially culminate in erasure from existence as with the humans who will die in hell (Ezekiel 18:4, 2 Peter 2:6).  Still, just as the fate of fallen humans is destruction unless they repent and commit to Yahweh/Christ, it would not follow that demons cannot or will not repent and rededicate their allegiance to God.  Satan entering the lake of fire as punishment does not mean that God never extends him or any other demon an offer of reconciliation; if this was to happen, then the verses about his defeat and potential death in hell would only necessitate that he refuses to repent and chooses irrationality and arrogance that damns him to punishment.  This is fully compatible with what the Bible does say.