[2] In the Mabinogi, Rhiannon is a strong-minded Otherworld woman, who chooses Pwyll, prince of Dyfed (west Wales), as her consort, in preference to another man to whom she has already been betrothed.

[5] This connection with Epona is generally accepted among scholars of the Mabinogi and Celtic studies, but Ronald Hutton, a historian of paganism, is skeptical.

Pwyll, the prince of Dyfed, has accepted the challenge of the mound's magical tradition to show a marvel or deal out blows.

Rhiannon characteristically rebukes him for not considering this course before, then explains she has sought him out to marry him, in preference to her current betrothed, Gwawl ap Clud.

Rhiannon rebukes Pwyll a second time for his rash promise, but provides the means and the plan to salvage the situation.

She instructs Pwyll to enter the hall dressed as a beggar and humbly request Gwawl fill a certain 'small bag' with food.

Terrified of being put to death, the women kill a puppy and smear its blood on Rhiannon's sleeping face.

However, as the end of the story shows, Pwyll maintains her state as his queen, as she still sits at his side in the hall at feasting time.

Reunited with Rhiannon the child is formally named in the traditional way via his mother's first direct words to him Pryderi a wordplay on "delivered" and "worry", "care", or "loss".

In due course Pwyll dies, and Pryderi rules Dyfed, marrying Cigfa of Gloucester, and amalgamating the seven cantrefs of Morgannwg to his kingdom.

Thunder and magical mist descend on the land leaving it empty of all domesticated animals and all humans apart from the four protagonists.

Returning to Dyfed, Manawydan and Pryderi go hunting and follow a magical white boar, to a newly built tower.

The magician Llwyd ap Cilcoed is forced to release both land and family from his enchantments, and never attack Dyfed again.

When Rhiannon first appears she is a mysterious figure arriving as part of the Otherworld tradition of Gorsedd Arberth.

When undergoing her penance, Rhiannon demonstrates the powers of a giantess, or the strength of a horse, by carrying travellers on her back.

Patrick Ford suggests that the Third Branch "preserves the detritus of a myth wherein the Sea God mated with the Horse Goddess.

Proinsias Mac Cana's position is that "[Rhiannon] reincarnates the goddess of sovereignty who, in taking to her a spouse, thereby ordained him legitimate king of the territory which she personified.

[11] These include Not For All The Gold In Ireland (1968) by John James, where Rhiannon marries the Irish god Manannan.

Nevertheless, despite having little accurate knowledge of the original Rhiannon, Nicks' song does not conflict with the canon, and quickly became a musical legend.

In the Robin of Sherwood story "The King's Fool" (1984), Rhiannon's Wheel is the name of a stone circle where Herne the Hunter appears to the characters.

[16] Rhiannon is included in various Celtic neopaganism traditions since the 1970s, with varying degrees of accuracy in respect to the original literary sources.

In the fantasy world of Poul Anderson's Three Hearts and Three Lions, there is a "University of Rhiannon", where magic is taught.