Hello Muzungu256,
"One of the heads of the beast appeared to be fatally wounded. But the mortal wound was healed, and the whole world was astonished and followed the beast." - Rev.13:3
"The seven heads are seven mountains on which the woman sits. They are also seven kings. Five are fallen, one is, and the other has not yet come; but when he does come, he must remain for only a little while. - Rev.17:9-11
"The beast that was, and now is not, is himself an eighth king. He belongs to the other seven and is going into destruction."
"They had as king over them the angel of the Abyss, whose name in Hebrew is Abaddon and in Greek is Apollyon (that is, Destroyer)."
The word "Beast" is used to represent both that last day kingdom, as well as the ruler of that kingdom, which is that beast who once was, now is not and yet will come. Those seven kings mentioned were a succession of kings, where at the time that John was receiving this information from the angel five had already fallen and number six was ruling "one is." The seventh king had not yet come and was therefore future to John, but is in the past to us.
The beast who once was, now is not and yet will come, refers to the following:
Once was = The beast once was out in the world and not in the Abyss
Now is not = The beast is currently not in the world, but is in the Abyss
And yet will come = The beast is currently in the Abyss and will be coming out of it again
The designation of "beast" is referring to the fallen angel currently in the Abyss, whose name is Abaddon/Apollyon and will be coming up out of the Abyss at the sounding of the 5th trumpet/1st woe. That this beast/fallen angel "once was" is most likely in reference to him being a power behind some political or military leader in the past, in the same manner as the prince of Persia who delayed the angel sent to Daniel, which was speaking of the angelic prinipality behind the human prince of Persia. In the same way, when this angel comes up out of the Abyss, he will be the empowerment behind the antichrist, that man of lawlessness. He is the same one who will kill the two witnesses when he comes up out of the Abyss.
We know that the beast is referring to the ruler of that last day kingdom, which will be the antichrist who will be empowered by that angel who comes up out of the Abyss:
"But the beast was captured, and with him the false prophet who had performed the signs on his behalf. With these signs he had deluded those who had received the mark of the beast and worshiped his image. The two of them were thrown alive into the fiery lake of burning sulfur." - Rev.19:20
When the Lord returns to the earth to end the age, the beast and the false prophet, "the two of them" will be captured and thrown "Alive" into the lake of fire. This is obviously speaking about two individuals who will be thrown into the lake of fire and not a kingdom.
All that said, this antichrist/beast will be that head, that eighth king who receives the fatal wound. The Greek word behind Fatal or mortal infers a "death stroke," i.e. it is not something that is survivable, which he does survive, which is why the inhabitants of the earth will be in awe of him. This will be apart of the miracles, signs and wonders that is meant to deceive the inhabitants of the earth in support of his claim of being God. At the same time, that second beast, who is also referred to as the false prophet, will be performing miracles, signs and wonders on behalf of the first beast, i.e. to give the first beast credibility in his claim of being God (2 Thes.2:4)
Therefore, the beast that receives the fatal wound, is not referring to the kingdom of Rome and its revival, but that beast that comes up from the Abyss who once was in the world, now is not and yet will come.
