In my study on the Antichrist Tradition (Part 3), I mentioned the possibility, accepted by many commentators, that the book of Revelation is drawing upon the legend of Nero’s return (Nero redivivus). The emperor Nero (r. 54-68 A.D.) was a notorious figure already in his own lifetime, as the historians of the period (Tacitus, Suetonius, et al) amply document. In response to rumors that he was responsible for the great fire in Rome, Nero instigated a persecution of Christians in the city, during which many were put to death (cf. Tacitus Annals 15.44). This would leave an indelible impression on believers, for whom Nero would remain in memory as the persecutor of Christians. Evidence for imperial persecution (arrests and executions) of believers during the reigns of the subsequent emperors (such as Domitian) in the 1st and early 2nd centuries is uncertain at best. Even under Nero, the period of persecution was brief, and more or less limited to the city of Rome. It wasn’t until much later, in the 2nd and 3rd centuries, that widespread, state-sponsored persecutions took place.
For early Christians, the role of the emperor itself was representative of impiety and wickedness, especially as the establishment of the imperial cult throughout the provinces emphasized all the more the traditional pretensions to deity intrinsic to ancient kingship (cf. the “wicked tyrant” motif in Part 1). Nero’s character and behavior added a particularly monstrous layer of wickedness to the figure of the Roman emperor, which would greatly influence how first-century Christians viewed imperial rule (compare how Paul speaks of it, prior to Nero). In some ways, this had been prefigured by the reign of Gaius (Caligula) some years earlier, but outside of the specific context of the persecution of believers.
By all accounts, Nero died by his own hand (committing suicide, cf. Suetonius, Nero 49.3-4) in 68 A.D. However, rumors soon took hold that Nero had not actually died, but had gone into hiding—perhaps in the East (among the Parthians), waiting for the opportunity to return and reclaim the throne. In the twenty or so years after his death, a number of Nero-pretenders appeared on the scene (Tacitus Histories 2.8-9; Suetonius Nero 57; Dio Cassius Roman History 66.19.3), and rumors doubtless persisted for a number of decades after that.
It is possible to understand the idea of Nero’s “return” in a figurative sense, in terms of his cruelty and tyranny being repeated in subsequent Emperors; on comparisons between Domitian and Nero, cf. Juvenal Satires 4.38; Pliny the Younger Panegyricus 53.4; Philostratus Life of Pythagoras 7.4.1 (Koester Revelation, p. 571). This is probably closer to how the book of Revelation makes use of Nero (and the Nero-legend)—as a type-pattern for the wicked ruler of the end-time, similar to that of the earlier emperor Gaius (Caligula) and the Seleucid king Antiochus IV Epiphanes (in Daniel 7-12 etc).
However, many commentators would see in the book of Revelation a more precise application of the Nero-legend, especially in the detail of the Sea-creature’s head that had apparently received a death-blow (“strike of death”) and was then healed/restored to life (13:3). The phrasing in 17:11 is thought to reflect this same imagery. The idea is that one of the heads (emperors) had suffered a mortal wound, but then recovered; on the assumption that this is an allusion to Nero, he would presumably be one of the first five emperors (heads) mentioned in 17:10. The eighth emperor, then, would be a demonic incarnation, in the form of Nero, or patterned after him—and, in this sense, he ‘returns’ from the dead. The visionary symbolism here may indeed have something like this in mind; certainly, the eighth ruler appears to be a direct (personal) manifestation of the forces of evil (cf. also on 2 Thess 2:3-12 and the Ascension of Isaiah 4:2ff in Part 3).
The Nero-legend would seem to feature in several eschatological passages in the Sibylline Oracles (cf. the survey in Part 2). This is rather clear, for example, in 4:119-24, 137-9—a great king’s flight from Italy, into the land of the Parthians, from whence he returns leading a great army. Nero also seems to be primarily in view in 5:28-34, 137-51, 214-27, 361-71; these verses include the idea that the wicked king flees from Rome (‘Babylon’), and, ultimately, on his return, will seize and destroy the Temple in Jerusalem (which the emperor did in 70 A.D.). Also worth mentioning is the detail in 3:63ff, when Beliar (= Belial), at the end-time, will appear, coming “from the Sebastenoi [Sebasthnoi/]”, which has sometimes been identified with the Sebastoi, the house of the emperor Augustus. This could refer to the idea that Beliar will be manifest/incarnate as a Roman emperor, and could apply to Nero (as well as any other early emperor). The incarnation of Satan/Belial (or a comparable evil Spirit-being) was certainly a component of the developed Antichrist Tradition, as mentioned and discussed in Part 3.