The story of Blodeuwedd tells of how a young woman was created by two magicians. They were Math and Gwydion, to be the wife of Lleu Llaw Gyffes, who had been condemned by his mother to have no human wife. But Blodeuwedd, the woman they made, is unfaithful to her husband, who then kills her lover. Blodeuwedd ends up being turned into an owl, condemned to fly only at night and to live ostracized by all the other birds of the air.
The Children of Arianrhod
Gwydion presented his sister Arianrhod to Math. He made the young woman step over a magic wand to test her virginity. But as she stepped over the wand, she dropped two small children. The first was called Dylan, but the second boy remained unnamed, as Arianrhod insisted that he would have a name only when she was ready to give him one. She then placed two more taboos on her son.
The tricks of Gwydion
Gwydion dealt with the first taboo— not naming the boy—by tricking his sister into calling him Lleu Llaw Gyffes (“Bright One of the Skilful Hand”). Her second taboo was that he would not bear arms until she was ready to arm him, but again Gwydion tricked her, and she equipped her son. Finally, she declared that her son would never have a human wife. This time Gwydion sought the help of Math, and together the pair used their magical powers to make Lleu a beautiful wife from the flowers of the broom, meadowsweet, and oak. The woman they created was called Blodeuwedd.
The treachery of Blodeuwedd
Blodeuwedd proved faithless. She took a lover, Gronw Pebyr, and the pair plotted to kill Lleu. Blodeuwedd tricked Lleu into revealing the only circumstances under which he could be killed, and then she placed him in the perfect position, leaving Gronw to strike the final blow. But as the spear pierced him, Lleu turned into an eagle. He was restored to human form by Gwydion, then found Gronw and killed him. As punishment for her part, Gwydion turned Blodeuwedd into an owl.