NIV
Revelation 17:10 They are also seven kings. Five have fallen, one is,
the other has not yet come; but when he does come, he must remain for only a little while.
It appears that the translators of the NIV equate the beast "yet to come" in Revelaiton 17:8b with king 7. They actually made a mistake, because the world is not going to wonder when king 7 arrives. Instead, the world is going to wonder when they see king 7 killed, and comes back to life as king 8, the beast king.
They are called kings, not beasts. The beast just means a king that is not a normal human.
There are only 7 heads and none of them come back from the dead. Satan is one of the heads, as he is the dragon. Satan was never an earthly king over an empire. Satan always was, but never was a king. When he is given a kingdom it will be a beast kingdom, because Satan is not a human, but an angel. The 8th kingdom is the 42 months mentioned in Revelation 13.
The 7th kingdom is not part of this dragon beast at all. There are only 7 heads, not 8 heads. The 6th Kingdom is the current condition on earth. It is mortally wounded because the church is the mountain that fills the earth, especially since the Reformation which dealt that mortal wound.
No earthly empire has been ruled by a single nation since the 10 toes. There have been the beast of the lion, bear, eagle, and leapord. The 5 fallen kingdoms were Babylon, Medes and Persians, Greece, Romans, and the 10 toes.
The 7th Kingdom happens at the Second Coming, when Jesus sets on the throne in Jerusalem. That rule is finalized at the 7th Trumpet.
"And the seventh angel sounded; and there were great voices in heaven, saying, The kingdoms of this world are become the kingdoms of our Lord, and of his Christ; and he shall reign for ever and ever."
Yes, that 7th kingdom can be interrupted by Satan's 42 months. Revelation 19 is the reclaiming of the 7th kingdom after Satan's 42 months as the 8th kingdom.
The marvelous recovery of the 6th head is the removal of the church at the 6th Seal. Yet this recovery is during the GT of the first 6 Trumpets. Jesus and the angels will be on earth during these judgments. The 6th Kingdom will only experience a very short come back, and will officially be over at the 7th Trumpet.
The 7th head is not killed to become the 8th king. The heads represent kingdoms not literal people. Except the 7th head, the main head of the dragon is Satan, not a human at all. Satan is the dragon mixing his ideology into the 6 earthly kingdoms.
The lady riding this beast is symbolic of Jerusalem throughout time and her relationship with the 6 heads or kingdoms. If Satan is given 42 months, he will sit on the throne in Jerusalem that Jesus set up per Matthew 25:31.
Satan can and does constantly ascend out of the pit. That is Satan's home. Satan can still ascend to heaven and is the accuser of the brethren, just as in Job. That has never changed since the Garden of Eden, as Satan is also referred to as "that old serpent" in Revelation 20:2.
Satan is held in check by the Holy Spirit and the church on the earth. Satan has not been bound in the pit, the last 2 millennia. Only during the Day of the Lord will Satan be bound in the pit. There will be a false prophet and a beast as part of this 8th kingdom that lasts for 42 months. But Satan is the head, the actual king of this kingdom not some human. Satan is also referred to as a beast, because Satan is not human. Only the FP is human, as the other entity is called a beast and not human either.
If you claim the dragon is both Satan and 6 other kingdoms, then those kingdoms are historical, and no longer exist. 5 of those heads do not even matter today, even if Greece, Persia, Rome, and Iraq could be part of the equation. John says 5 are fallen, thus no longer viable. The third of the stars, those cast to earth, have never been viable, until they are released from the pit at the 5th Trumpet. That is the first woe. There may be a king who stands up after the church is removed, but he will have constant competition with Jesus and the angels Jesus brings to earth when He arrives. But the dragon with 7 heads is still the beast out of the sea, and the scarlet beast of Revelation 17. The only new addition are ten earthly leaders who have never been kings with authority who come out of the aftermath of the 6th Seal. They work hard during Satan's 42 months to remove all that is associated with the religious aspect of mystery Babylon. They bring their armies to Armageddon to stop Jesus taking back the 7th kingdom. They are all killed at Armageddon.