The period know as The Millennium, in biblical terms is the thousand year reign of Christ here on earth. Millennium comes from the Latin word mille, which means a thousand and annum which means year. This period of time is very controversial because it is only found in the book of Revelations and is only mentioned once. (Read Rev. 20:1-6)
At this period Satan is tied and is thrown in prison where he wouldn’t be able to deceive nations. After this 1000 year period he will be released again for a short while and he goes out to deceive the nations in the four corners of the earth – Gog and Magog and gathers them for battle. Here they march across to God’s city. But they are killed by fire and Satan is finally thrown into the lake of burning sulfur.
Rev. 20:7-10 “When the thousand years are over, Satan will be released from his prison and will go out to deceive the nations in the four corners of the earth — Gog and Magog — to gather them for battle. In number they are like the sand on the seashore. 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. 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.”