The is difference of opinions whether Domitian or Nero was in power at the time John received Revelation.
The early Church father Irenaeus confirmed Domitian as Roman emperor when John was at Patmos. Tertulian said John was exiled for his testimony under Domitian (see "
The Prescription Against Heretics" by Tertulian, ch.36). Eusebius in
Ecclesiastical History, Book 3) credits Domitian as ruling during the time of John on Patmos. Irenaenus in
Against Heresies, Bk.5, Ch.30) said John had the Revelation vision at the close of Domitian's reign.
The 7th king will become the 8th king, after the 7th king is killed and comes back to life.... and continues for a short space (of 42 months in Revelation 13:5)
The 7th beast king will be Satan himself, working miracles upon this earth in plain sight. He is not killed and then comes back to life. The only time Satan will be destroyed is by God's Fire at the end of Christ's future "thousand years" reign. And when that destruction happens, Satan will have been loosed after Christ's "thousand years" reign as the 8th beast king to deceive the unsaved nations one final time, as written at the end of Rev.20.
What you are thinking about is the
"deadly wound" of Rev.13. It is upon one of the
"seven heads" which are "
mountains" (geographic areas of the earth), and not upon the beast king. That
"deadly wound" was upon one of Lucifer's beast kingdom "
seven heads" described in Rev.12:3-4. For the Rev.13 beast kingdom that
"deadly wound" suffered upon one of its
"seven heads" will be healed.