1.From Paroria to Kilifarevo
Hesychasm — the teaching of inner prayer and stillness — entered Bulgaria through Gregory of Sinai, who spent much of his life at Paroria, in the Strandzha border mountains. The area was full of robbers who threatened the hermits, and Gregory sent one of his closest disciples, Theodosius of Tarnovo, to the Bulgarian tsar. Ivan Alexander endowed the community with a large sum of money, sheep and oxen, a village and a lake for fishing, and around 1345–1346 Theodosius was sent to Tarnovo again for help.
After Gregory's death around 1346 his disciples scattered — many of them to Athos. Theodosius travelled through the Holy Mountain, Thessaloniki and Berrhoia, and then, according to his Life, withdrew with his disciple Romanos into the Emona mountains near Mesembria. In the end he returned to Bulgaria and, in the mountains at Kilifarevo, far from Tarnovo and other towns, set up a series of cells. His fame drew monks, and soon some fifty of them had turned the "desert" into a kind of town.
2.Theodosius' Monastery (c. 1350)
Theodosius did not like to stay long in one place and took a lively interest in church affairs in the world. He returned to Tarnovo, and around 1350–1351 the tsar paid for a new monastery for him near the capital — Kilifarevo, with a rule modelled on the one Gregory of Sinai had brought from Sinai. Theodosius became its abbot. Together with the monastery of the Virgin at Paroria and the Dragalevtsi monastery, Kilifarevo was among the houses built with Ivan Alexander's help.
Under Theodosius and with his companions Romanos (Romil) and the future patriarch of Tarnovo Euthymius, Kilifarevo became a spiritual hearth whose influence soon reached beyond the tsardom. Here worked the so-called Kilifarevo literary school; some scholars also link to it the Tomić Psalter, whose choice of miniatures — the Retribution, the Second Coming, the transience of human life — carries an anti-heretical message.
3.Against the Heresies
The second half of Ivan Alexander's reign saw strong heretical movements. With the active involvement of Theodosius, whom the Lives present as their inspirer, the tsar convened two anti-heretical councils — in 1350 and 1359–1360 — which condemned Bogomils, Barlaamites, Adamites and Jews; the second met in the newly built royal palace in Tarnovo. The Life of Theodosius by Patriarch Kallistos of Constantinople compares him to a brave commander going into battle. Around 1361 it was probably through Theodosius that Kallistos addressed his reproaches to the church of Tarnovo.
Kilifarevo's legacy outlived its founder. His disciple Euthymius spent years in Constantinople and on Athos and in the last three decades of the fourteenth century was the undisputed leader of spiritual and literary life in Bulgaria. The monastery itself lay within the fortified zone around the capital — the fortress at Kilifarevo stood not far from it.