There is an interesting historical intrigue about the Byzantine roots of the Russian royal line. It goes through Sophia Palaiologina, a Byzantine Princess. After the Fall of the Byzantine Empire she was transferred to Rome, and Vatican planned to establish a bridge between the papal see and Russia using her marriage. But the wedding happened, she immediately dropped ties with Rome. The Russians did not allow the papal Legate Anthony, who was in the escort of the Princess, to enter Moscow carrying the Latin cross before him. Another Byzantine person in the escort was man named Constantine, who later was tonsured a monk in Russia. He became a friend with St. Nil Sorsky, a renowned hesychast. Cassian in monasticism, he lived godly life, founded a monastery and became a Saint himself, St. Cassian the Greek.

Savior the Pantocrator icon, made in Constantinople. It was brought to Russia by Sophia Paleologina, grandmother of Ivan the Formidable. Sophia's father in the third artwork photo.

A historical movie about the Byzantine line of the Orthodox monarchs of Russia and other events of that century https://www.amazon.co.uk/Sophia-Russian-Historical-Ac..