Saints Gregory and Cassian of Avnezh lived in asceticism at the River Sukhona in the Vologda land. On June 15, 1392 they died as martyrs at Avnezh monastery during an incursion by Tatars.
The relics of the monastic martyrs were uncovered in the year 1524. In 1560, with the blessing of Macarius, Metropolitan of Moscow and All Russia (+ 1564), Barlaam, the Igumen of Makrisch monastery, wrote an account of these holy martyrs.