Venerable Peter, Tsarevich of the Horde

Venerable Peter, Tsarevich of the Horde, was a Chinggisid prince, a nephew of Khan Berke of the Golden Horde. His Life, the "Tale of Peter, Tsarevich of the Horde", survives in more than 120 manuscripts and is regarded by scholars as largely reliable.

According to the Life, Bishop Cyril II of Rostov visited the khan's court and spoke of St Leontius of Rostov and the miracles at his relics. The young prince was so moved that he followed the bishop to Rostov, and after Berke's death he was baptized Peter. Under Bishop Ignatius (1262–1288) the Apostles Peter and Paul appeared to him in a dream on the shore of Lake Nero and told him to build a church there. The prince of Rostov, probably Boris Vasilkovich, granted him land and became his sworn brother; Peter married the daughter of a Horde nobleman living in Rostov.

In old age, after his wife's death, Peter took monastic vows. By church tradition he died in 1290 and was buried at the church of the Holy Apostles, around which the Petrovsky Monastery of Rostov grew up. His veneration spread in the mid-16th century, when his Life entered the Great Menaion Reader and a service was composed. He is commemorated on 30 June (13 July) and on 23 May (5 June) in the Synaxis of the Saints of Rostov and Yaroslavl.