‘And death and Hades were cast into the lake of fire. This is the second death, even the lake of fire.'
This demonstrates that the primary purpose of the lake of fire is to burn up that which is at enmity with God's final purposes. It also demonstrates that we must not literalise the scene. Death and Hades are not existing entities, they are ideas (compare Revelation 6:8), as is much of what lies behind the beast (false empire) and the false prophet (false religion). These are all destroyed. This is the death of death the last enemy (1 Corinthians 15:26). But it is only the fallen spiritual beings who are described as facing an unending future of remorse and misery.
Note with regard to men how the phrase ‘the dead' is constantly stressed. The resurrection of those who are not His is not a joyous occasion of new life but of those who are dead while they are alive, and when, like death and Hades, they are thrown in the lake of fire they are not thrown in ‘alive' as were the beast and the false prophet. They are thrown in as ‘the dead'. There is no reason to doubt that they too will be destroyed and utterly consumed. It is the second death for it is final. It is the death of the soul. After this there is no resurrection.