This is the Final judgement of God. It will happen at the end of the Millennium Kingdom, after Satan is let loose for a short time and his final attempt at a revolt against God fails yet again.
Satan and all his followers will be cast into hell at this point, to suffer torment alongside the antichrist and his false prophet, for all eternity. God will remake the Heaven and Earth and an new era will dawn, free from any sin.
“And I saw a great white throne, and him that sat on it, from whose face the earth and the heaven fled away; and there was found no place for them. And I saw the dead, small and great, stand before God; and the books were opened: and another book was opened, which is the book of life: and the dead were judged out of those things which were written in the books, according to their works. And the sea gave up the dead which were in it; and death and hell delivered up the dead which were in them: and they were judged every man according to their works. 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.”
REVELATION 20:11-15 (KJV, HOLY BIBLE)
Recommended material:
- Bible: Revelation 20
- Bible commentary: What is the last judgement?