The last empire comes out of the Roman empire. The Antichrist is part of this Revived Roman Empire, but he is also separate from it. In King Nebuchadnezzar's great statue, Rome was the legs of iron. But the last empire is represented as feet of clay mixed with iron, having 10 toes. It is the last and final Satanic empire. The beast, the Antichrist, is one of the 10 kings. He becomes one of them by subduing 3 of them. Yet he is different, unique. In a real sense, he is an eighth kingdom.
The beast, appears to be a compilation of all of the prior 4 kingdoms:
He is separate, but he is also part of the last dynasty. He is at its head. The last dynasty exists before the beast appears and he supplants 3 of the 10 kings, so that there remain 7 kings and he is an eighth king, ruling over this last dynasty.