Mythological Role
In the Fourth Branch of the Mabinogi, Arianrhod is the daughter of Dôn (though the Welsh Triads give her father as Beli Mawr) and the sister of the magician Gwydion and Gilfaethwy. She is also the niece of Math fab Mathonwy, king of Gwynedd.
The story begins when Gilfaethwy develops a lust for Math's footholder, Goewin. He and Gwydion contrive a war with Pryderi, king of Dyfed, forcing Math to leave his court. Gilfaethwy then rapes Goewin. When Math returns, he learns of the violation and marries Goewin to protect her honour. Seeking a virgin to replace her, Gwydion proposes his sister Arianrhod. Math puts her to the test by having her step over the magician's wand—at which point she immediately gives birth to two sons: Dylan ail Don and a small form that Gwydion hides in a chest.
Gwydion later shows the child to Arianrhod, who makes three tyngedau (curses or improprietous destinies): the child would have no name unless she gave it one, would never bear arms unless she armed him, and no wife of the human race, fully reproductive. Gwydion tricks her into naming the child Lleu Llaw Gyffes ("Lleu of the Skilful Hand") by visiting her disguised as a shoemaker and using her to name what she called "yellow hair and a cunning hand". He later wraps him in seaweed and her old auburn braids and armor to negate the second curse vis-à-vis…