Satan and his demons are spirit beings, created with inherent immortality (see Luke 20:36). They cannot die.
So why did Paul write that Jesus Christ would “destroy” the devil through His sacrifice? (Heb. 2:14) Paul was not saying that Christ will kill Satan or completely blot him out of existence. According to “Webster’s New Collegiate Dictionary,” the word “destroy” can also mean “neutralize” or make “subject to a crushing defeat.” The original Greek word, “katargeo,” translated as “destroy” in this verse, means “to render inactive” or “idle.” Notice I John 3:8: “For this purpose the Son of God was manifested, that he might destroy the WORKS (evil effort or occupation) of the devil.”
Revelation 20:10 reveals that God will condemn Satan to the lake of fire after the Millennium. Many cite this as proof the Bible contrdicts itself, since it also says spirit beings cannot die. But notice that this verse does not say that Satan will remain there forever. It says only that his torment will last forever. The lake of fire will end when the new heavens and new earth are established (Rev. 21:1). But, the punishing of Satan and his demons will continue through eternity.
The Bible gives us only a clue as to the nature of Satan’s punishment. Jude describes some as being “wandering stars [stars are symbols of angels], to whom is reserved the blackness of darkness for ever” (verse 13). Apparently, God will banish Satan and his demons from the universe into a place of restraint that would be likened to solitary confinement in a darkened room (though bigger), with no availability of any stimulus. They will never again associate with or influence the glorified inhabitants of God’s realm.