Caer Ibormeith

Caer Ibormeith was a princess, the child of Prince Ethal Anbuail from the fairy mound of Sid Uamuin in Connacht. For more than a year, the god Óengus dreamed of her standing by his bed, but she always vanished when he tried to touch her. Her nature was tied to the festival of Samhain: every second year, she took human form for a single day starting at sunset, then changed back into a swan for the following twelve months until the next Samhain. Searching for the woman from his dreams, Óengus went to the lake called the Dragon’s Mouth.

There he found one hundred fifty girls linked in pairs by chains, and among them was Caer. He was told he could marry her only if he could pick her out while she was a swan. Óengus chose correctly, then transformed himself into a swan as well. The pair flew together to his home, the palace of Brú na Bóinne on the River Boyne near Slane. As they traveled, they sang so beautifully that everyone in Ireland fell asleep for three days and three nights.

Caer married Óengus of the Tuatha Dé Danann and later became the foster mother of Diarmuid. In a different version of the story, Caer alone was bound by one hundred thirty chains, rather than being chained with other swans.