Who Rhiannon is
Rhiannon enters the first branch as a woman in shining gold, riding a pale horse near Pwyll's mound in Dyfed. His riders cannot catch her, however hard they chase, but she stops when Pwyll himself calls to her. Her arrival brings the Otherworld into a story about marriage, promises and honor.
What Rhiannon wants
Rhiannon wants to marry Pwyll rather than Gwawl, the man her family has chosen for her. She tells Pwyll her wishes directly, making her own choice central to their relationship. Gwawl brings trouble to their wedding, where a clever trick involving a magic bag helps Pwyll overcome him.
Rhiannon and the others in the story
Rhiannon's marriage to Pwyll leads to the birth of a son, but the child disappears on the very same night. Her frightened women smear her with blood and accuse her, turning the loss into an ordeal of false blame.
Questions
Who is Rhiannon in The Mabinogion?
Rhiannon is a woman of the Otherworld who chooses Pwyll as her husband and later suffers unjust blame.
Why does Rhiannon stop for Pwyll?
She stops when he calls to her, after his riders fail to catch her. She then tells him that she would rather marry him than Gwawl.