The Beast and the False Prophet are men that are inhabited by demonic spirits. The Beast is referred to as a man and yet in Revelation he is said to ascend from the abyss.
7 And when they shall have finished their testimony, the beast that ascendeth out of the bottomless pit shall make war against them, and shall overcome them, and kill them. ( KJV)
What we can conclude is that the men who are inhabited by these spirits will burn up in the fire and the demonic spirits will be in the tormented. However, again this is not eternal, the passage acutally reads, unto the ages of the ages. We also know that this is not eternal because the Lake of Fire, Gehenna will eventually, be restored and made holy to the Lord.
38 Behold, the days come, saith the LORD, that the city shall be built to the LORD from the tower of Hananeel unto the gate of the corner. 39 And the measuring line shall yet go forth over against it upon the hill Gareb, and shall compass about to Goath. 40 And the whole valley of the dead bodies, and of the ashes, and all the fields unto the brook of Kidron, unto the corner of the horse gate toward the east, shall be holy unto the LORD; it shall not be plucked up, nor thrown down any more for ever.
( KJV)
There's no way that Gehenna can be a place of eternal torment as it will be restored and made holy to the Lord.