Ahez

Of unknown origin and meaning, albeit a connection to Welsh aches, a word denoting the sound of the water clashing on the shore, has been suggested. In Breton legend, Ahez is always described as the daughter of King Gralon, sometimes described as a sorceress, enchantress, fairy or giantess, and often, though not always, considered identical with Dahud.
Gralon was the king of Kêr-Is, a city built on land reclaimed from the sea and rich in commerce and the arts which was protected from the water by a dike with a gate that was opened for ships during low tide. Unlike her pious father, Ahez was a wayward and frivolous young woman, an unrepentant sinner. One night, while the king slept, Ahez stole the keys, a symbol of royalty, from her father, either to allow her lover inside for a banquet or after being persuaded to do so by her lover. Believing she was opening the city gates, the princess mistakenly opened the gates of the dike and the sea inundated the city. Everyone in the city was killed, apart from Ahez and Gralon who had been woken up by the voice of a saint who urged him to flee. The king took his daughter with him, but as the water was about to overtake Gralon, a voice called out: "Throw the demon thou carriest into the sea, if thou dost not desire to perish." The father threw the daughter off the horse's back and was saved. When the waves swallowed her, Ahez became a mermaid who continues haunting the sea. To this day, she can be seen combing her golden hair and singing sad songs.