He entered monastic life as a youth and was a disciple of St Sergius of Radonezh. After years of monastic obedience he was ordained to the priesthood, then founded a monastery on the shores of Lake Priluki, whose rule followed that of the Lavra of St Sergius. Saint Demetrius, who was exceptionally handsome, always concealed his face behind his monastic veil and never conversed with women. Once a noblewoman, driven by curiosity, managed to catch sight of his face in church. She immediately fell paralyzed to the ground. The Saint asked her ‘My child, why did you want to gaze at the face of a sinner who has long been dead to the world?’ He then gave her some words of instruction in the spiritual life and sent her away healed.
In time St Demetrius became so renowned in Russia that the flow of visitors burdened him and he retreated to an uninhabited area to live as a hermit, until he was found out and made abbot of a nearby monastery. He kept a constant fast, living only on prosphora and water. In his own lifetime the Saint was known for his gift of prophecy, his care for the poor, and his healings. Once his brother sought his blessing to trade with the pagans in the far north. He made a good profit there and asked for a blessing to return. This time the Saint would not give his blessing, but his brother went anyway, and was killed by pagans.
Toward the end of his life St Demetrius withdrew into solitude in his cell. One day the brethren noticed a wonderful aroma of incense coming from his cell and knew that he had departed this life for heaven. After his repose he continued to work countless miracles, healing illnesses (especially the plague), and driving away invaders.