He opposed the Roman Catholic Church to the point of pillaging abbeys and monasteries and accumulating a large treasure during a period of eight years (1140–48).
[1] Born near Loudéac to a noble family, Eudon, as he was originally called, was briefly an Augustinian friar taking up a hermit's life in the Brocéliande (Brécheliant).
Around 1140, during the reign of Conan III of Brittany, Éon took up residence in the abandoned priory of Moinet, but he did not remain there long.
Éon's band of followers attacked the rich and redistributed their wealth amongst themselves, eventually dressing themselves in the highest finery and eating lavishly.
Under Pope Eugene III, the Council of Reims in 1148 condemned Éon's movement as heresy (hérésie éoniste).