Mission to the KhazarsKhazars Khaganate
Byzantine Emperor Michael III and the Patriarch of Constantinople Photius (a professor of Cyril's at the University and his guiding light in earlier years), sent Cyril on a missionary expedition to the Khazars who had requested a scholar be sent to them who could converse with both Jews and Saracens. The trip, unfortunately, ended in failure if it had intended to convert the Khazars to Christianity as the Byzantines only managed to baptise around 200 of them. The Khazaria state eventually adopted Judaism instead. Cyril did bring back souvenirs, though, said to be the relics of the exiled 1st century CE Bishop of Rome, Saint Clement.