Take notice that the beast referred to as an individual is cast into the lake of fire along with the false prophet. The second beast (false prophet) prompts everyone to worship and take the mark of the first beast.
Also, Rev. 16:13 references 3 individual entities; dragon (Satan), antichrist, false prophet.
Lastly, the devil/Satan is cast into the lake of fire where the beast (antichrist) and false prophet (religious leader) are.
Rev 19:19-20
"And I saw the beast, and the kings of the earth, and their armies, gathered together to make war against him that sat on the horse, and against his army.
20 And the beast was taken, and with him the false prophet that wrought miracles before him, with which he deceived them that had received the mark of the beast, and them that worshipped his image. These both were cast alive into a lake of fire burning with brimstone.
Rev 16:13
And I saw three unclean spirits like frogs come out of the mouth of the dragon, and out of the mouth of the beast, and out of the mouth of the false prophet.
Rev 20:10
And the devil that deceived them was cast into the lake of fire and brimstone, where the beast and the false prophet are, and shall be tormented day and night for ever and ever.