Rev 20:7 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.
After the 1000 yrs is complete, satan is released for a short season. Why? Not really sure, however all those who went thru the millennium, who never really had a choice, satan will be seeking to add to his final rebellion. Its very short lived as God sends out a fire and devours this rebellion and satan joins the antichrist and the false prophet in the lake of fire. Never to cause havoc again. God is very methodical & detailed in His plan. We will not understand the big picture this side of eternity. Its so beyond us. Yet what is clear, He has a plan & He is in full control. He is orchestrating His plan while working in each individual life. I ask, HOW? He is so far beyond my finite little mind. I can barely keep my bearings around my small world of influence. Try 6 plus billion people on this planet.