Erispoe was Duke of Brittany from 851 to his death. After the death of his father Nominoe, he led a successful military campaign against the Franks, culminating in his victory at the Battle of Jenglan
The pages of the Redon cartular in which the Île-aux-Moines is mentioned for the first time (copy). This charter preserves and indicates how Erispoë gave the parish called Chaer, with the outfits that depend on it and their settlers, namely Avaellon, Clides and Villata, with its vineyards and meadows, and the island called Crialeis, that is to say Enesmanac, as a fief to the monks of the abbey of Saint-Sauveur, as alms for his soul and for the kingdom of God.