Revelation 20:7-10

⁷ Now when the thousand years have expired, Satan will be released from his prison ⁸ and will go out to deceive the nations which are in the four corners of the earth, Gog and Magog, to gather them together to battle, whose number is as the sand of the sea. ⁹ They went up on the breadth of the earth and surrounded the camp of the saints and the beloved city. And fire came down from God out of heaven and devoured them. ¹⁰ The devil, who deceived them, was cast into the lake of fire and brimstone where the beast and the false prophet are. And they will be tormented day and night forever and ever.

This is the final battle between God and Satan.

There are a few interpretations here. 

One is that the “rest” will live again after a thousand years and be deceived by Satan once again.  All will battle against the saints and their world.  Then God destroys them with fire.  The devil is cast once again into the lake of fire and brimstone except this time it is forever more.

Another is that in the millennium there will be saints with their glorified bodies and the martyred saints with non-glorified bodies.  This second group can and will have children.  These persons, like all persons, will have the ability to say yes or no to Jesus.  Outwardly they will say yes, but inwardly many will say no and when the time comes to be able to rebel they will.

Lastly, there is the idea that all saints are in their glorified bodies that live 1,000 years and is free from pain and disease, but even still, they will be turned away from God in their hearts during this time.

Whichever it is, the question remains, “Why does God allow Satan to be loosed one more time?”  The best answer seems to be twofold: 1) To demonstrate the evil intention of Satan that consume him now and forever. 2) To reveal that even in a near perfect environment with no Satanic temptation, man is capable of and willing to rebel against his gracious and loving God.

“Gog and Magog” is a reference to Ezekiel 38-39.  This is a reference to the enemies of God among the nations of the world. 

As Satan and those who rebel with him come to battle against the new city, they are vaporized in an instant with fire.  Like the battle of Armageddon, the battle is really an execution.  At this, Satan is bound forever.