Pwyll first met Rhiannon, when she appeared as a beautiful woman dressed in gold and riding a white horse. Pwyll sent his horsemen after her, but she was too fast. After three days, he spoke and Rhiannon told him she would rather marry him than her fiance, Gwawl. After a year and a day, he won her from Gwawl with her assistance. Their first son disappeared while in the care of several of Rhiannon's ladies-in-waiting. To avoid the blame, they smeared blood from a puppy on Rhiannon, who was asleep.
The child appeared in the court of King Teyrnon, whose mares had just given birth but the foals had disappeared. Teirnon watched his stables and saw a mysterious beast coming to take the foal; Tiernon stopped the beast and found the child outside the stable. He and his wife adopted him. The child grew to adulthood in only seven years and was given the foal which had led Teyrnon to the stable. Teyrnon realized who the child was and returned him to Pwyll and Rhiannon, who named him Pryderi (worry).
Pryderi married Cigva and became King of Dyfed after his father died. He then invited Manawydan (his stepfather) to live with him in Dyfed. Soon, Dyfed turned into a barren wasteland and only Rhiannon, Pryderi, Cigva and Manawydan lived. Manaywdan and Pryderi, while out hunting, saw a white boar which they followed. Pryderi and his mother, Rhiannon, touched a golden bowl that the boar led them to and became enchanted. Manawydan and Cigva were unable to help them until they captured a mouse which was actually the wife of Llwyd, Rhiannon's enemy (seeking revenge for her treatment of Gwawl), and the spell was lifted.