Gabriel lived a life of asceticism in the eleventh century Kratovo on Mt. Osogovo, where he built a church dedicated to the Holy Archangel Michael. Several other monks joined him, and this was the advent of the Lesnovo monastery. It remains still unsolved whether Gabriel founded a monastery or whether it was founded on the spot close to his hermitage. Very little is known of this original monastery and the first and only mention of the old monastery comes only from 1330 in a chronicle by its monk Stanislav, a famous writer. During the reign of Emperor Ivan Asen II (r. 1218–1241) the relics of the saint were transferred from the monastery to the then capital of Bulgaria — Tarnovo, and placed at the Church of St. Apostles on Trapezitsa. After the Ottoman invasion of Bulgaria at the end of the 14th century, the traces of the holy relics of Saint Gabriel were lost.