And the sea gave up the dead who were in it, Death and Hades gave up the dead who were in them, and they were judged, each one of them, according to what they had done. Then Death and Hades were thrown into the lake of fire. This is the second death, the lake of fire. And if anyone's name was not found written in the book of life, he was thrown into the lake of fire. (Revelation 20:13-15 ESV Emphasis mine) We often understand hell and death as being eternal things. Once you're dead, you're dead and once someone goes to hell, they stay there forever. According to this verse, something very different happens in the end. "Death...[is] thrown into...the second death". This would mean that death dies. Death is done away with. And wouldn't this hold the same for hell? Hell dies. And then, those not written in the book are thrown into this second death as well, and, if death is done away with and hell too, wouldn't these people be done away with as well? If this is the case, then doesn't that mean that hell and death are not eternal?