Crimea

Basileia Krimaike Crimean Empire

One of the Golden Horde khans converted to Christianity in the early 1400s in order to cement an anti-Ottoman alliance with Lithuania. He sheltered the Byzantine court in exile, nominally acknowledging the emperor's greater sovereignty. At its height in the late 1400s this empire was really quite vast, but it could not withstand the Ottoman onslaught and was reduced to a much smaller area. The current imperial dynasty is actually originally of Italian origin, though most of their actual ancestors are Russian. They remain pretty shadowy and disengaged from the affairs of state - the Tatar ruling class has done a good job keeping them out of the way.