Jamieson, Fausset and Brown on Revelation 17:11

11. beast that ... is not--his beastly character being kept down by outward Christianization of the state until he starts up to life again as "the eighth" king, his "wound being healed" (Re 13:3), Antichrist manifested in fullest and most intense opposition to God. The "he" is emphatic in the Greek. He, peculiarly and pre-eminently: answering to "the little horn" with eyes like the eyes of a man, and a mouth speaking great things, before whom three of the ten horns were plucked up by the roots, and to whom the whole ten "give their power and strength" (Re 17:12, 13, 17). That a personal Antichrist will stand at the head of the Antichristian kingdom, is likely from the analogy of Antiochus Epiphanes, the Old Testament Antichrist, "the little horn" in Da 8:9-12; also, "the man of sin, son of perdition" (2Th 2:3-8), answers here to "goeth into perdition," and is applied to an individual, namely, Judas, in the only other passage where the phrase occurs (Joh 17:12). He is essentially a child of destruction, and hence he has but a little time ascended out of the bottomless pit, when he "goes into perdition" (Re 17:8, 11). "While the Church passes through death of the flesh to glory of the Spirit, the beast passes through the glory of the flesh to death" [Auberlen].

is of the seven--rather "springs out of the seven." The eighth is not merely one of the seven restored, but a new power or person proceeding out of the seven, and at the same time embodying all the God-opposed features of the previous seven concentrated and consummated; for which reason there are said to be not eight, but only seven heads, for the eighth is the embodiment of all the seven. In the birth-pangs which prepare the "regeneration" there are wars, earthquakes, and disturbances [Auberlen], wherein Antichrist takes his rise ("sea," Re 13:1; Mr 13:8; Lu 21:9-11). He does not fall like the other seven (Re 17:10), but is destroyed, going to his own perdition, by the Lord in person.