His Crimean campaign is mentioned in only one source, the Russian version of the Life of St. Stephen of Sougdaia (Stephen of Surozh in Russian), tentatively dated to the 15th or 16th centuries.
Vasily Vasilievsky, who was the first to publish this manuscript in the 19th century, reasoned that the core of the narrative might stem from the Early Middle Ages, reflecting a vague memory of some 10th-century Russo-Byzantine conflict.