Any human being thrown into the lake of fire will be destroyed and will not be tormented for eternity.
"The devil, who deceived them, was cast into the lake of fire and brimstone where the beast and the false prophet are [or were cast, as many acknowledge this should be rendered]. And they will be tormented day and night forever and ever" (Revelation 20:10).
Does this verse say that these two end-time individuals, the Beast and False Prophet, will be tormented for eternity?
The Beast and False Prophet are human beings. While still alive, they will be cast into the lake of fire. "Then the beast was captured, and with him the false prophet who worked signs in his presence, by which he deceived those who received the mark of the beast and those who worshipped his image. These two were cast alive into the lake of fire burning with brimstone" (Revelation 19:20).
We see from Malachi 4:1-3 and Mark 9:47-48 that any human being thrown into the lake of fire will be destroyed. He will perish. But he will not be tormented for eternity.
Revelation 20:10 is speaking of Satan the devil being cast into the lake of fire at the end of Christ's 1,000-year reign. Reference to the Beast and False Prophet being cast in is only parenthetical here—as they will have died when that happened 1,000 years earlier. They will not still be burning there. Thus being tormented "forever and ever" applies principally to Satan—and presumably to his demonic cohorts as well (compare Matthew 25:41).
Furthermore, it should be pointed out that the Greek phrase translated "forever and ever" here, eis tous aionas ton aionon, literally means "unto the ages of the ages." While this might mean for eternity, it could also mean until the culmination of the ages, which would allow for an ending point soon after the casting into the fire.