Mabon the Enchanter, Mabon the Sorcerer
An enchanter in the Post-Vulgate Merlin continuation and the Prose Tristan who learned sorcery from Merlin. There is no reason to doubt that he is derived from the Welsh Mabon.
Mabon captured and imprisoned Bors. Fearful of Erec, who by his mother’s enchantment was immune to magic, Mabon sent Bors to kill him. Erec defeated Bors and freed him from Mabon’s service. In another episode, Gawain apparently fought against Mabon over a fairy named Marsique. Gawain, equipped with the Scabbard of Excalibur, was victorious.
Mabon began a rivalry with his friend, Mennonas, for the love of the lady Grysinde. He sent an enchanted ship, called the Ship of Joy, to find Tristan, intending that Tristan should fight Mennonas as Mabon’s champion. Tristan arrived on the ship, engaged Mennonas in combat, and killed him.
Sources
Post-Vulgate Suite du Merlin | 1230-1240
Post-Vulgate Queste del Saint Graal | 1230-1240
Prose Tristan | 1230-1240