Magician and wise man in Arthurian legend .
In Geoffrey of Monmouth 's History of the Kings of England , Merlin was an adviser to King Arthur, with magical powers that recalled his Celtic origins. Later narratives made him a prophet of the grail and gave him credit for the idea of the Round Table. In Sir Thomas Malory 's Morte Darthur he brought Arthur to the throne and served as his mentor throughout his reign. His downfall was linked to his infatuation for an enchantress, who imprisoned him after learning the magic arts from him.