Ahes was a legendary Breton princess and she was known by many names: Dahud, Dahut, Ahés and Ahé. Only later did she become a siren, sending fishermen to their deaths in the waves that consumed her in her moment of greatest folly.
She was the daughter of Gradlon (or Gralon, Grallo, King of Ker-Ys) and the sorceress Malgven. Her father built for her Ys, a wonderful city by the seashore because Ahes loved the ocean. Though she was very beautiful, she was also spoiled and riddled with insatiable appetites for men. Each night, she took a new lover into her bed until one day, a strange prince appeared. He had eyes of flame and was clad from head to foot in red (some say black). People whispered that the fearsome prince was the enemy of Gradlon.
The king's confessor, Guénolé, urged Ahes and her lover to curb their drunken revelries. But Ahes was the daughter of a sorceress and wicked, leading her people into drunken debauchery. She ignored the warning that would have prevented the destruction of Ys.
The prince, citing love, demanded that Ahes give him the keys that opened the city’s floodgates and she, bewitched, complied, taking the key from around her father’s neck. With nothing to stop him, the prince opened the sluices, drowning the beautiful city of Ys. Most of the people were drowned. Gradlon fled from the waters on horseback, with his daughter and Guénolé on the crupper behind. But the waters threatened to overtake the trio, for the horse could not take three and Guénolé was well aware of who was responsible for the city’s demise.
The confessor bade his king, “Throw your daughter into the sea!” Gradlon knew that he had no choice and flung Ahes, shrieking, into the rushing water, where she was quickly consumed. The waves immediately receded, but the city of Ys was submerged, never again to resurface. According to the legend, though, Ahes did not die. Instead, she was transformed into a siren, a lovely maiden luring sailors to their dooms.
Ahes’ legend most likely evolved from the mythos of A Hes, a British sea goddess. Her story is often associated with that of Morgan le Fay, though the association is a tentative one.
The legend of the sunken city of Ys (Ker-Ys) circulated as early as the 16th century and had many localized incarnations.
The submerged city is said to have become part of the Bay of Dourarnenez.