Late Latin Koine Greek (395–610) Medieval Greek (610–1453)
Republican monarchy Absolute monarchy
Status in OTL:
The Byzantine Empire or Eastern Roman Empire (known to its inhabitants as the Roman Empire) was the continuation of the Roman Empire during the Middle Ages, centered on its capital of Constantinople, and ruled by Emperors in direct succession to the Roman Emperors. The Empire preserved Roman legal traditions, but embraced substantial Hellenization, i.e. Greek custom. The term "Byzantine Empire" postdates the Empire itself, and was popularized by historians during the 16th-19th centuries.
The Empire itself existed for roughly a thousand years; there was no precise "founding" date, but rather a series of decisions made by the Roman Empire that saw the Byzantine Empire eventually split off and grow into its own entity. The Empire finally fell in the 15th century to the Ottoman Empire, with Constantinople surrendering in 1453.
However, its main rival remained Persia to the east, an empire roughly as strong and one of the three great powers, along with China, of the known world. Byzantium and Persia clashed, sometimes openly, but mostly maneuvered quietly to gain an advantage over the other.
Under Constantine V, the Byzantine Empire had a harsh policy of Iconoclasm, silently resisted by communities such as Abrostola in the Anatolic Theme. For these reason, the Abrostolans were determined to handle crime in their community on their own, rather than attract unwanted attention from any Imperial official.
In 597, the Roman Empire was under threat from the barbarian Avars. When the enemy recruited powerful supernatural forces to advance their cause, the Christian Romans summoned countering forces with unlikely help from the ancient Greek past.