After the Millennium period, the devil is released for a short time, so that he can go and deceive the nations and try to thwart God’s plan. Many people joined him and tried to battle God’s people. The devil’s people were defeated and he was thrown into the lake of fire forever.
God showed up literally on His Great White Throne and the heavens and the earth fled from His presence. He made all the dead stand before Him and judged them according to what they had done and threw all the evil doers into the lake of fire.
Matthew 25:31 “When the Son of Man comes in His glory, and all the holy angels with Him, then He will sit on the throne of His glory. 32 All the nations will be gathered before Him, and He will separate them one from another, as a shepherd divides his sheep from the goats. 33 And He will set the sheep on His right hand, but the goats on the left. 34 Then the King will say to those on His right hand, ‘Come, you blessed of My Father, inherit the kingdom prepared for you from the foundation of the world: 35 for I was hungry and you gave Me food; I was thirsty and you gave Me drink; I was a stranger and you took Me in; 36 I was naked and you clothed Me; I was sick and you visited Me; I was in prison and you came to Me.’
37 “Then the righteous will answer Him, saying, ‘Lord, when did we see You hungry and feed You, or thirsty and give You drink? 38 When did we see You a stranger and take You in, or naked and clothe You? 39 Or when did we see You sick, or in prison, and come to You?’ 40 And the King will answer and say to them, ‘Assuredly, I say to you, inasmuch as you did it to one of the least of these My brethren, you did it to Me.’
41 “Then He will also say to those on the left hand, ‘Depart from Me, you cursed, into the everlasting fire prepared for the devil and his angels: 42 for I was hungry and you gave Me no food; I was thirsty and you gave Me no drink; 43 I was a stranger and you did not take Me in, naked and you did not clothe Me, sick and in prison and you did not visit Me.’
44 “Then they also will answer Him, saying, ‘Lord, when did we see You hungry or thirsty or a stranger or naked or sick or in prison, and did not minister to You?’ 45 Then He will answer them, saying, ‘Assuredly, I say to you, inasmuch as you did not do it to one of the least of these, you did not do it to Me.’ 46 And these will go away into everlasting punishment, but the righteous into eternal life.”
Revelation 20:7 When the thousand years are over, Satan will be released from his prison 8 and will go out to deceive the nations in the four corners of the earth—Gog and Magog—and to gather them for battle. In number they are like the sand on the seashore. 9 They marched across the breadth of the earth and surrounded the camp of God’s people, the city he loves. But fire came down from heaven and devoured them. 10 And the devil, who deceived them, was thrown into the lake of burning sulfur, where the beast and the false prophet had been thrown. They will be tormented day and night for ever and ever.
Revelation 20:11 Then I saw a great white throne and him who was seated on it. The earth and the heavens fled from his presence, and there was no place for them. 12 And I saw the dead, great and small, standing before the throne, and books were opened. Another book was opened, which is the book of life. The dead were judged according to what they had done as recorded in the books. 13 The sea gave up the dead that were in it, and death and Hades gave up the dead that were in them, and each person was judged according to what they had done. 14 Then death and Hades were thrown into the lake of fire. The lake of fire is the second death. 15 Anyone whose name was not found written in the book of life was thrown into the lake of fire.