: The winner of the final battle on Judgment Day will ultimately claim Creiddylad.
From my initial search, I found that "Gwythr" is a Welsh word that means "white lord" or "white god". It's also the name of a figure in Welsh mythology. However, without more context, I'm not sure if this is related to the paper you're interested in.
: Gwyn and Gwythr must fight every May Day (Calan Mai). gwythr
Gwythr is a client king or champion who owes allegiance to Arthur. His inclusion in Arthur’s retinue (in some lists of Arthur’s warriors) places him among the teulu (war-band) – but he is never a Round Table knight in the later French tradition.
“Gwyn ap Nudd was prompted to carry off Creiddylad, daughter of Lludd Llaw Eraint. Then Gwythyr ap Greidiol was greatly angered, and he warred against Gwyn. But Gwyn overcame him and took him prisoner.” : The winner of the final battle on
Possibly – his name may derive from gwyth (“vehemence, fury”) + gwyr (“man”), suggesting a personified force. He may be a euhemerized solar deity.
Other seasonal folklore like the "Four Branches"? However, without more context, I'm not sure if
Gwythr represents the force that must fight, even if it cannot ultimately win. His annual combat is a vegetation myth: summer (Gwythr) battles winter (Gwyn) each spring, and the outcome shifts, but the cycle never ends until the apocalypse.
The central myth involving Gwythr is a tragic romantic rivalry. Gwythr was betrothed to Creiddylad, the daughter of Lludd Llaw Ereint. However, before the marriage could be consummated, Gwyn ap Nudd—the King of the Otherworld (Annwn) and leader of the Wild Hunt —abducted her.
In Culhwch and Olwen , King Arthur intervenes to stop the mutual destruction of the two armies. He decrees a settlement that creates the rhythm of the seasons:
In modern neopaganism and literary fantasy, Gwythr is often invoked as a symbol of the High Summer sun, contrasting the darker, chthonic energy of Gwyn ap Nudd. He represents the active, martial force of the day, as opposed to the shadowy mystery of the night.