The legends of his life are known through Beunans Meriasek, a Cornish language play known from a single surviving manuscript copy dated 1504, and a few other sources.
Conan Meriadoc, the legendary king of Brittany at the time, wanted to arrange a political marriage for him, but Meriasek preferred to renounce his inheritance and become a priest.
He assisted the Viscount in dealing with brigands who infested his lands by bringing down the fire of heaven upon them; in gratitude he founded three fairs at Noyal at the saint's request.
He is reputed to have healed many lepers and disabled people, to have driven off the highwaymen of Josselin through prayer, to have made water spring from solid rock, and to have calmed a storm.
He was elevated to become bishop of Vannes[4] but continued to wear a hair shirt, practise asceticism, and minister to the poor.