Welsh Otherworld figure of the Mabinogion First and Third Branches; scholarly-consensus Welsh manifestation of the Gaulish horse-goddess Epona and the Irish goddess Macha. Her name reconstructs to the Brittonic *Rīgantonā ("Great Queen") — a clear theonym pattern. Comes from Annwn (the Welsh Otherworld) on a shining white horse moving at a steady pace yet impossible to catch by the fastest mortal horses; chooses Pwyll, prince of Dyfed, as her consort, breaking her arranged contract with Gwawl. Defeats Gwawl through the bag-trick. Mother of Pryderi by Pwyll. Suffers the famous trial of being unjustly accused of infanticide (her newborn was abducted by a black-clawed apparition while her nursemaids slept; they smeared her with the blood of a slaughtered puppy and accused her of having killed and eaten the child); her punishment was to sit at the gate of Pwyll's castle for seven years, telling visitors what she had allegedly done and offering to carry them on her back as a beast of burden — a punishment-as-horse-form that scholars read as preserving her horse-goddess identity through the Christian-era redaction. Vindicated when Pryderi is restored. After Pwyll's death, married to Manawydan fab Llŷr (the Welsh cognate of the Irish Manannán mac Lir). Suffers further trials in the Third Branch during the Desolation of Dyfed (a seven-year vengeance-enchantment by Llwyd, magician-friend of Gwawl). The Birds of Rhiannon (Adar Rhiannon) — three magical birds whose song wakes the dead and puts the living in a dream — sing for the seven-year Harlech feast in the Second Branch and are mentioned in Culhwch ac Olwen as one of Ysbaddaden's anoethau (impossible tasks). Per the registry's standing precedent (Mongán case in Irish tradition: medieval-literary divine-paternity claim about a historical-or-legendary figure passes strict-criterion under the literary-tradition reading), Rhiannon's scholarly-consensus deity-status combined with her Mabinogion narrative-functional treatment as Otherworld-figure who marries a mortal prince makes her the divine parent for Pryderi's strict ½ demigod classification.