Gwydion was a member of the court of King Durin in prehistoric times. He was the leader of the conspiracy against his liege, and Gwydion himself was the one who impaled Durin with a stake.
The members of the conspiracy began to fight for power immediately after Durin's death. Gwydion was among the first to die, being killed by a mob of angry citizens furious with the conspirators.
When he died, Gwydion became the Magician, the personification of one of the Major Arcana. His form is that of an anthropomorphic fox. Later, after he makes a deal with Ardath Dastagir, his eyes turn purple and he gradually loses his animal appearance, becoming more human.