"And the BEAST which was and is not, is himself also an EIGHTH,
This verse restates verse 8. This is the same BEAST described in Revelation 13:1-8. The conclusion then is that this is the antiChrist himself.
"which was" refers to his mortal life, "is not" refers to his apparent dearth, and "is himself" denotes his 'resurrection' into his supermortal life. To Jews still looking for the Messiah, the antiChrist through his imitation of Jesus' life, crucifixion, and resurrection is very convincing. Jesus himself had warned this would happen (Mark 13:14-23). Ironically, for Jews to accept the antiChrist as the Messiah, the antiChrist must either be a Jew or an exceptional impostor.
To be the EIGHTH means that not only does the antiChrist wholeheartedly participate in the wickedness of all the seven kingdoms, but also is the embodiment of this wickedness in superhuman form. The dragon (Revelation 13:4) has given him a personal pride and arrogance which will set him apart from all other mortals. See the "little horn" of Daniel 7:8.
and is one of the SEVEN,
In the previous verse, we defined the SEVEN as abstract concepts. They could just as easily be socioreligious entities such as Protestants, Catholics, Moslems, Buddhists, Jews, and such. We are not given a clue what the seven "kingdoms" are; so the reader/student of the Revelation MUST ever be aware of the world's religious landscape. Since the Bible is so closely tied to the Jews, God's chosen people, true believers must ever watch events in Israel. Interestingly, even the secular press instinctively knows this and gives disproportionate news coverage about Israel
and he goes to DESTRUCTION.
After "remaining a little while" (previous verse), this simple sentence marks the end of the BEAST. Revelation 19:20 identifies the location of this DESTRUCTION.
This verse completes the triplet of verses concerning the seven heads of the BEAST.