Gwenhwyfach

No mythological origin narrative is preserved in the cited sources. Gwenhwyfach appears in medieval Welsh narrative lists and triads as a sister of Gwenhwyfar; later commentators have conjectured (on the basis of name-forms) that she may represent a lesser or darker counterpart to Gwenhwyfar, but this is interpretive and not attested as an origin myth in the surviving passages.

The surviving sources do not provide a physical description. She is attested only by name within lists (Culhwch and Olwen) and triadic notices that recount interpersonal enmity; no bodily, costume, or iconic features are recorded in the cited materials.

No supernatural powers are ascribed in the primary references cited. Her notable attributed behavior is a single violent action — a slap to her sister — which the Triads list among the "Three Harmful Blows of the Island of Britain" and which is said to have caused the Strife of Camlann. Otherwise she functions as a named human antagonist within Arthurian court material.