Saint Theodosius the Bulgarian and his disciple Romanus. StTheodosius began his exploit in the city of Viddino, at the Nikolaev monastery. After the death of the igumen Job he settled near Trnovo, then the capital city of Bulgaria, at the Holy Mountain monastery of the Most Holy Theotokos in search of a spiritual guide.

He left the Holy Mountain monastery and for a long time went from monastery to monastery. Finally, he learned about the desert monastery called "Concealed" where in pursuit of asceticism St Gregory of Sinai (August 8) had moved from Athos. St Theodosius found in him an experienced guide of the contemplative life. St Gregory taught, "Before death we lay in Hades; whoever does not recognize sincerely that he is a sinner, and that the beasts and cattle are more pure, is more wicked than the demons, having become their obedient slave."

The wilderness monastery of St Gregory of Sinai suffered often from robbers. The abbot sent St Theodosius to the emperor Alexander with a request to defend the monastery. The pious Bulgarian Tsar, at the request of the ascetic, provided him with the means to surround the monastery with strong walls with towers, and made the monastery secure with land and cattle.

During his final journey to Trnovo on an errand for the abbot to the Tsar, a nobleman asked St Theodosius to take him along to the monastery. The holy ascetic brought him to St Gregory of Sinai. This was Romanus, who became the sincere and beloved disciple of St Theodosius.

After the death of St Gregory of Sinai (November 27, 1347), St Theodosius refused to become head of the monastery, and he left the monastery with his disciple Romanus for solitary struggles. They founded a monastery on a hill near Trnovo, afterwards called Theodosiev.

St Theodosius was famous as a zealous defender of Orthodoxy against many heresies, especially the Bogomils, Judaizers and Messalians. Their false teachings were especially pernicious. The Patriarch and the Tsar rendered great help to St Theodosius in the struggle with the heretics. In addition to this, the holy ascetic translated Greek writings into Slavonic.

In 1360, he became grievously ill. Wishing to see his friend St Callistus once more, he went to him at Constantinople, entrusting the direction of the monastery to his disciple Romanus.

St Theodosius died at Constantinople on February 17, 1362. His disciple St Romanus became head of the monastery.