History of Europe
In 395 Theodosius I, who had made Christianity the official religion of the Roman Empire, would be the last emperor to preside over a united Roman Empire. The empire was split into two halves: the Western Roman Empire centred in Ravenna, and the Eastern Roman Empire (later to be referred to as the Byzantine Empire) centred in Constantinople. The Roman Empire was repeatedly attacked by Hunnic, Germanic, Slavic and other “barbarian” tribes (see: Migration Period), and in 476 finally the Western part fell to the Heruli chieftain Odoacer.
Last Roman Emperor
The legend is based on the "Apocalypse of Pseudo-Methodius", which was, after the Book of Daniel and the Book of Revelation, "the most widespread apocalypse story in Europe". It proposes a different Last Emperor from the previous figure, who fought against religious enemies, and introduced the conflict with Islam: he will "go forth against them [the enemies of the faith] from the Ethiopian sea and will send the sword and desolation into Ethribus their homeland, capturing their women and children living in the Land of Promise". After conquering his enemies he would travel to Jerusalem and relinquish his power on the Mount of Olives. The Last Emperor was further developed in the writings of Adso of Montier-en-Der, whose "Libellus de Antichristo" (ca. 954) was a popular biography of the Antichrist, whose coming was preceded by the rise of a Frankish ruler (the continuation of the Roman Empire); this Last Emperor would voluntarily give up his power and die, after which the Antichrist comes to power. Another important impetus came from the oracles of the Tiburtine Sibyl, first recorded in Latin around the year 1000; its legend proved particularly adaptable to rulers all over Europe, containing as it did a list of emperors and kings leading up to the Last Emperor which could be revised or added to as political and dynastic circumstances required. It still had great currency in the fifteenth century.