Which historical empire's fall forms the backdrop of Assassin's Creed Revelations?

The fall of the Byzantine Empire forms the historical backdrop of Assassin's Creed Revelations.

The game is set mainly in Constantinople during the early sixteenth century, when Ottoman power dominates the city and the Byzantine imperial tradition has already been displaced. Ezio travels there while pursuing Altaïr's legacy and searching for keys connected to the Masyaf fortress.

The Byzantine Empire is also called the Eastern Roman Empire, and its final capital, Constantinople, fell to the Ottoman forces of Mehmed II in 1453. That historical transition is central context for the game's setting, but Revelations does not depict the empire's final conquest directly as its main event.

Revelations was released in 2011 and is the concluding chapter of Ezio's main trilogy. It also includes playable sequences featuring Altaïr, linking the Renaissance storyline to the events of the first Assassin's Creed.