The story of Rhiannon is one of
many myths contained in the Mabinogion, a Welsh collection of mythology.
Rhiannon was the daughter of a god, Heyvedd the Old, and she was set to marry
Gwawl, another god. But Rhiannon was in love with Pwyll of Dyfed, a mortal man
whose adventures are described in the first part of the Mabinogion. Rhiannon and
Pwyll marry, and seem happy at first, until Gwawl comes down from the Bright
World and tries to kill their newborn son, Pryderi. Rhiannon's maids, unable to
find the boy they were supposed to be guarding, cover Rhiannon's dress with a
puppy's blood and accuse her of murdering her son. Pwyll, listening to his
subjects rather than his wife, forces Rhiannon into a terrible punishment -- she
must stand on a block at the entrance to Dyfed and tell everyone that she is
standing there because she killed her child. She must then offer all who enter
the kingdom a ride on her back, as though she were a horse.