Author: Kyria d'Oreyn
Queen Rhiannon is a historical figure (CoT, Prologue).
She once showed up in the White Tower and submitted a request for which she took the answer to all but granted, but she was set straight for her behavior. A wall-hanging in the White Tower supposedly depicts her humbling (ACoS, Ch. 24; CoT, Prologue).
"'Elayne, if you believed, why did you announce who you were like Rhiannon at the Tower?' She rather liked that; according to the story, what Queen Rhiannon got was far from what she had wanted." (Nynaeve to Elayne; A Crown of Swords, Chapter 24)