And death and hell were cast into the lake of fire. This is the second death.
And whosoever was not found written in the book of life was cast into the lake of fire [Rev. 20:14–15].
And death and Hades were cast into the lake of fire. This is the second death even the lake of fire. And if any were not found written in the book of life, he was cast into the lake of fire.
You will notice that in my translation I have changed “death and hell were cast into the lake of fire” to “death and Hades were cast into the lake of fire.” Sheol or hades (translated hell in the New Testament) is the place of the unseen dead and is divided into two compartments: paradise and the place of torment (see Luke 16:19–31). Paradise was emptied when Christ took the Old Testament believers with Him at His ascension. “Wherefore he saith, When he ascended up on high, he led captivity captive, and gave gifts unto men. (Now that he ascended, what is it but that he also descended first into the lower parts of the earth? He that descended is the same also that ascended up far above all heavens, that he might fill all things)” (Eph. 4:8–10). Christ did two things: He gave gifts to men down here, but He also took with Him to heaven those Old Testament saints who had died and were in the place called paradise. But the place of torment will deliver up the lost at the judgment at the Great White Throne. All who stand at this judgment are lost, and we are told that they are cast into the lake of fire, which is the second death. The Lord also called it “outer darkness.” We believe that this is symbolic of something worse than literal fire or outer darkness. It is eternal separation from God, for death means separation.

“Death,” the great final enemy of man, is finally removed from the scene. No longer will it be said, “In Adam all die” (see 1 Cor. 15:22). Death is personified in this case, for it is man’s great enemy. In the Old Testament we read: “I will ransom them from the power of the grave; I will redeem them from death: O death, I will be thy plagues; O grave, I will be thy destruction: repentance shall be hid from mine eyes” (Hos. 13:14).
And Paul writes: “The last enemy that shall be destroyed is death…. O death, where is thy sting? O grave, where is thy victory?” (1 Cor. 15:26, 55).
“Hades,” the prison of lost souls, is likewise cast into the lake of fire. The lost are no longer in hades but in the lake of fire. This is where Satan, the wild Beast, the False Prophet, and their minions were consigned. If man will not accept the life of God, he must accept the only other alternative: eternal association with Satan. God never created man to be put in this place, but there is no other place for him. Hell was created for the Devil and his angels. I take it that it is a place where God never goes. The second death means eternal and absolute separation from God.
McGee, J. Vernon: Thru the Bible Commentary. electronic ed. Nashville : Thomas Nelson, 1997, c1981, S. 5:1061-1062