Morgan Le Fey is a misguided Fairy Princess who unseals Celestin. Celestin is using Morgan's body because he doesn't have one of his own and they apparently share the same mind.
Morgan once fell in love with a human, who both went to the Judgement Gate to test their devotion. Morgan later learns that she didn't hold enough faith within herself. She thought that one day, her and the human would go their separate ways. This forced the couple to live apart. Not accepting that these events were her own fault, she releases Celestin to help get revenge.
At the end of the movie, Morgan lets go of everything and stays at the Judgement Gate to tell anyone that goes there that there were a couple at passed the test.