What lie does Satan use to deceive the people after the millennium?
Satan deceives post-millennium multitudes by telling them they have had it good but would rather be like God. That lie entices them to rebel, and they fall for it. As their rebellion mounts, God intervenes, and fire from heaven devours them. This occurs after the thousand years when Satan is released for a little while.
Les explains that after the thousand-year millennium ends, Satan is released for a little while. The length is unknown; in God's timing it could be several years, but it is a while. During that short period, Satan deceives the multitudes with the lie: "Granted you've had it good, but wouldn't you rather be like God?" They fall for it. As their rebellion mounts, God moves in, and they are zapped off the scene. They compass the camp of the saints and the beloved city, and fire comes down from God out of heaven and devours them; they are gone, wiped off the scene. Then the devil that deceived them is cast into the lake of fire and brimstone, where the antichrist and the false prophets are, and they are tormented day and night forever and ever. Les emphasizes there is no annihilation; it is a continuing thing, and no one should believe they will be burned up.
And shall go out to deceive the nations which are in the four quarters of the earth, Gog and Magog, to gather them together to battle: the number of whom is as the sand of the sea.