Rhiannon gives birth to a boy, Pryderi, and the child is abducted when his care-taking women fall asleep. To save themselves from punishment, the women smear animal blood on Rhiannon so that it will appear to Pwyll that she has killed their son. Pwyll is deceived by this cruel act and punishes Rhiannon harshly. It is not until years later when the child is discovered to be alive and is returned to his parents that Rhiannon is redeemed. The child has been named Gwri, or “Golden Hair,” by the people who had found him as a baby and had cared for him. Finally relieved of her worry, Rhiannon renames the child Pryderi (“Care”).

In the “Third Branch” of the Mabinogion, Pryderi has married Cigfa and has succeeded Pwyll as king of Dyfed. Rhiannon has married Manawydan, a son of Llyr. As is the Irish Manannan mac Lir, Manawydan is associated with rebirth. During a feast at Arbeth, the two couples are sitting in a cloud of mist on the magic throne mound. There is a clap of thunder before the mist clears and the couples find themselves in a totally deserted Dyfed. After two years of wandering, they make their way to Lloegyr (England), where Pryderi and Manawydan take work as saddlers, shoemakers, and shieldmakers.

When the four finally return to Arbeth, Pryderi disregards the warnings of Manawydan and allows himself to be drawn by a boar into a mysterious castle that has a fountain in which a golden bowl sits on a marble slab. Some have considered this to be the Cauldron of Plenty—the pot which supplies endless food—or even the Holy Grail sought by King Arthur’s knights. Pryderi loses speech and cannot release his hands when he grasps the cauldron. Rhiannon tries to rescue her son, but she, too, loses speech and is stuck to the cauldron. Mother and son disappear into a mist.

The perpetrator of these enchantments and the abduction of the hero and his mother is Llwyd, an associate or friend of the evil Gwawl. Manawydan and Pryderi’s wife Cigfa return to England as shoemakers, but eventually return to Arbeth to grow corn. When mice are discovered carrying the corn away, Manawydan captures the slowest of them and prepares to hang it on the throne mound, when a bishop turns up and reveals that the mouse is actually his wife. The bishop also reveals that he is actually Llwyd, and in return for his wife he puts an end to the terrible curses and spells that had enchanted Pryderi and his family.