Now the angel is speaking of the individual who will be the ruler of the kingdom yet to come. This phrase refers to the period of the reign of the Beast following his revival from his deadly wound. If his revival occurs near the midpoint of The 70th Week of Daniel, then this would refer to the last half of the week, the three and one-half years during which he is given authority: he was given authority to continue for forty-two months (Rev. Rev. 13:5+). This period is one of great turmoil since the Beast receives his power, throne, and authority from the dragon (Rev. Rev. 13:2+) and the dragon has great wrath because he knows that he has a short time (Rev. Rev. 12:12+). See Prophetic Year. See Events of the 70th Week of Daniel. See commentary on Revelation 17:8. He is an eighth kingdom in the sense that the seventh kingdom originally arrives as a global empire which shall devour the whole earth. Out of this seventh kingdom ten horns . . . shall arise (Dan. Dan. 7:23-24). The Beast himself shall rise after them (Dan. Dan. 7:25). After his revival, the ten horns give their authority to the Beast (Rev. Rev. 17:12-13+) and he reigns supreme and uncontested (Rev. Rev. 13:3+). In the final form of Gentile dominion, the self-rule of the Beast, he is an eighth king, but only hinted at as an eighth head here.1
If we look upon the Roman dictator as being the seventh, he becomes the eighth, the Antichrist at the time of the Satanic incarnation, and thereby becomes an eighth, who is thus out of the seven, since Satan is the cause of all of the others.2
In his mortal stage he is the seventh head; but in his superhuman stage he is the eighth king.3See #16 - Beast.
he is of the seven
He is of the seven in that his origin, both as a head and a horn (see below) is from among the other heads and horns: He is an eighth contemporary king ruling over the other seven kings who have submitted to his authority. Yet he is of the seven, for he is the seventh head of the chronological ruling governments. The term seven refers to the heads, while the term eight refers to the horns.4 And though he is an eighth king, there are not really eight, but only seven, for the seventh and the eighth are the same personage; therefore, it is said that the eighth is of the seven. 5 See #13 - Seventh King.
is going to perdition
See commentary on Revelation 17:8.
1 Fruchtenbaum sees mention of his eighth as pertaining to his relationship among the horns: Dan. 7:23]. . . . These ten kings are contemporary and rule together. But as was seen from Daniel seven, when the Antichrist begins to take control, he uproots three of the ten horns. He kills three of the ten kings, leaving seven for the remainder of the Tribulation period. The Antichrist is contemporary with these seven, making him an eighth.Arnold G. Fruchtenbaum, The Footsteps of Messiah, rev ed. (Tustin, CA: Ariel Ministries, 2003), 43. While he is indeed an eighth horn, the context of Revelation Rev. 17:11+ is discussing heads which are mountains which are kings. The ten horns do not yet enter the context until the next verse.