Note that after Adam, all man had to suffer death as a penalty for sin. Death in Scripture frequently means a separation. For a bodily death, a separation of soul and spirit from the body. For spiritual death, a separation from God.
Note that unlike man, the angels ahd been created without death. It has been summised from study of Scripture, that since Satan and the fallen angels have already been condemned to the Lake of Fire for all eternity, and that decision made in prehistory, that man's role in this affair is simply evidence testing in a cosmic appeal. Man essentially provides massive evidence in the angelic conflict that His judgment is not only immutable, but just.
In the case of angels, or other creatures, the issue of redemption assumes those creatures had sinned or had come into live as a consequence of sin. Just because God's grace provides a Kinsman-Redeemer for man, doesn't mean the relationship of other creatures with God is identical as Man's relationship with God.
Discovery or identification of 'aliens', especially when they fit the descriptions and characteristics of demons, by no means destroys the Word of God. On the contrary, many of the independently reported testimonies of such encounters are remarkably consistent with Scriptural settings of angelic attributes and conditions.
I said Spock, not Spooks.