With his mentor in 1371 Gregory made a pilgrimage to Jerusalem, where he was ordained a celibate priest, and on the way back St. John gave him the crosier of vardaped. In 1380 they moved to Apracunis monastery, which Gregory headed in 1388, after the death of his teacher, but by the latter’s blessing and popular vote. Two years later the saint returned to Tatev with his numerous followers. Remaining in constant ascension through prayer, St. Gregory, like the noonday sun, brightly illuminated with his radiance the Armenian Church. Many Greek and Latin orators came to listen to his speeches full of wisdom and broad knowledge. St. Gregory was called the second John Chrysostom and Gregory the Theologian.
None of the infidels dared to harm him, because they saw the great miracles that God performed through this man. The saint healed the ailing by laying of hands, cast out demons. Exhausted by fasting and wearing sackcloth, being constantly belted with a rope, he killed himself for this world while still being alive, thus becoming a man of great virtue and holiness.
Before his death, knowing of his imminent passing, the saint celebrated the liturgy, blessed his disciples and gave up his spirit glorifying the Lord.
To this day generations of scholars and theologians study the literary heritage of Saint John of Tatev. Few of his numerous works have survived - "The Book of Questions", "Vosceporik", Summer and Winter volumes of "Book of Sermons", numerous commentaries, and other writings, as well as two Gospels illustrated by the saint.