God: "I looked for someone to take a stand for me, and stand in the gap" (Ezekiel 22:30)
Why do we deny the possibility of redemption for fallen angelic beings?
1. There is no record of such in Scripture.
2. There is no record in Scripture of demonic repentance.
3. The impact of the cross on demons is always portrayed as judgment, never salvation (nowhere do we read of justification, forgiveness, redemption, adoption, regeneration, etc. being true of any angelic being).
4. Hebrews 2:14-17; Revelation 5:8-14.
The devil is not terribly frightened of our human efforts and credentials. But he knows his kingdom will be damaged when we begin to lift up our hearts to God.