Culhwch

Some time later, Culhwch had been arranged to marry his own stepsister, but he refused. Angry, his stepomother cursed him to marry no one but Olwen. Olwen's father, Ysbaddaden, was a vicious monster that would die if he was separated from his daughter. After many trials and tribulations, Culwch succeeded with the aid of Mabon and gained Ysbaddaden's powers and life.