They are all destroyed by God at that time. They, including Satan and his angels, are all consumed by fire. This is the final distruction of sin and sinners for all time. All of this is supported by the Bible in Daniel and Revelation if you look close enough. You will find that there is no hell fire that burns eternally.
Hell fire is just final for all eternity.
Think about it. It only makes sense. Eternal simply means final for all eternity. Also the human soul is not eternal it is gone at death and recreated by Christ at the resurrection. Also only makes sense.