Annwn, or Annwfn, is ruled by Gwyn ap Nudd or Gwyn, son of Nodons, a Briton god whose temple was at Lydney in the forest of Dean. He often appears among mortals to meddle in their affairs. Found at Arthur's court in Culhwch and Owen, where God is said to have given him dominion over the demons, "lest this world be destroyed." Folklore transforms him into the leader of the Wild Hunt, riding through the clouds raising human shades, along with the red-eared hounds of Annwn and occasionally by the undead Arthur himself.
There are various entry points into Annwn, namely Lundy Island and Glastonbury Tor. There is a legend of an itenerant Welsh saint named Collen entering Gwyn's palace within the Tor in order to banish him by sprinkling holy water around.
Contained within the alleged Book of Taleisin is "The Spoils of Annwn," an obscure, inauthentic Welsh poem dating from perhaps the tenth century. It is the tale of a raid on the part of Arthur and his knights through the underworld, questing for a magical, talismanic cauldron in the custody of nine maidens. Only seven survive this perilous expedition. Due to the pagan substance of the poem, it has been claimed to be a foreshadowing of later Grail Quests.The number nine relates to real groups of nine priestesses in pre-Christian, Celtic society. Geoffrey of Monmouth tells of a sisterhood of nine led by Morgan le Fay in his poetic Vita Merlini. The coven was located on the Isle of Apples, or Avalon, another otherworld sometimes identified with Annwn.