Extract and comment from Revelation Chp. 1.
(a)I am He that liveth, and was dead; and behold, I am alive for evermore, and have the keys of (b)death and Hell.*
(a) Christ defeated the last enemy at the cross, the completed work will be handed back to the Father at end of Millennial, (1Cor. 15:24).
*(b) The text reads "death and of Hell"; the Greek Haydes, (Str. 86, is “grave"). Hell is a Greek philosopher's concept, which originated in Babylon and was introduced into Roman Church teaching after AD 300 under Constantine and Helena, and later into Church of England and other groups. It has no basis in fact in the whole of Scripture in the Dante sense, and is almost certainly confused with the Lake of Fire in Revelation.
The Second death however is real, and is reserved for Satan, his angels and demons and all who follow Satan at any time, and who are not redeemed by Christ's blood sacrifice, see Rev. 20:14-15. Also, the references in Chp. 14:9,10 & 11, are often lumped together with the "Lake of Fire", in the false Hell concept, (see comments there). See: Hell; 20:13 (b).1:18 (b) and Lake of Fire and Brimstone; 20:10 (a) & 21:8 (b) & Hell;
The ref. in Isa. 66:24, is almost certainly refers to the "goats", of the "sheep and goat judgement", (Matt. 25), linking to "Bashan" of "Og" infamy; Deut. 3, Psm. 22:12 and Ezek. 39:18.
See: Soul and Spirit, The Error:
Sheep and Goat Judgement (Study)