Saint Pol

Saint Pol was one of the founding saints of Brittany. He came from the monastery at Llanwit Major in Wales and made his first stop on the island of Ouessant, where the town is still called Lampaul (holy place of Pol). He may have gone there deliberately to challenge a major centre of paganism. Once on the mainland his journey eastwards is echoed in names like Lampaul-Ploudalmezeau and Lampaul-Guimiliau.
Arriving near the current day St-Pol-de-Léon he was given land on the Ile de Batz by the local lord and there performed his famous feat of leading a dragon (using his bishop's stole) to the cliff edge and commanding it to dive to destruction into the sea. In the cathedral and elsewhere in St-Pol-de-Léon today, look out for many representations of St-Pol and/or his dragon. But you won't find any sign of a cliff at the Serpent's Hole on the Ile de Batz!