May Day, in Welsh myth, is the time of the annual battle between Gwyn ap Nudd, leader of the Wild Hunt, Lord of the Dead, and his followers, against those led by Gwythur ap Greidawl (son of "Scorcher"), for the maiden Creudylad.
It is such an old story, having its roots in bardic antiquity when stories were chanted, not written, that a number of differing versions exist and fragments have been woven into many other stories. There may be even more variations on the spelling of the primary players' names than there are of the story itself.
In probably the oldest and purest version of the story, there is an everlasting battle between Gwyn and Gwythyr, some say for the "love" of Creudylad, or simply for possession of her. The beautiful maiden Creudylad is the daughter of Lludd of the Silver Hand (son of Beli).
Some mythologers connect Lludd with Nuada of the Silver Hand, king of the Tuatha de Danaan. Shakespeare scholars identify Lludd as the model for King Lear and Creudylad as the original Cordelia. Gwyn and Gwythur appear in very early Arthurian tales, with Arthur intervening to stop the unending bloodshed by decreeing that the two fight only one day each year, on May Day.
Creudylad was betrothed to Gwythur ap Greidawl when she was carried off by Gwyn ap Nudd, Lord of the Underworld, King of Avalon. The yearly battle can be seen as symbolic of Summer fighting off Winter, with Creudylad standing in for the fertility goddess. Gwyn ap Nudd loses the fight in springtime and is confined to Glastonbury Tor, which has long had a reputation as a portal into the Underworld.
Gwythur son of Scorcher (the Sun), presides from Beltane to Samhain, the autumnal cross-quarter day of souls, when Gwyn once more emerges from the Tor and takes over this earthly realm.