Soon, however, the number of disciples who gathered around him necessitated the construction of adequate buildings, in which was instituted the monastic life, following the Rule of St. Benedict, and interpreted in a manner similar to the Cistercians.
The founder was Vitalis de Mortain, Canon of the Collegiate Church of St. Evroul, who, resigning his prebend to embrace an eremitical life under Robert of Arbrissel in the forest of Craon (Anjou), and leaving the latter, retired to the forest of Savigny (1105), where he built a hermitage.