Merlin

Merlin is a British wizard who was a mentor to King Arthur. At the very beginning of the episode, he sent him and the sorceress Mab  back a thousand years ago. When Arthur appeared in the past, the young Merlin, who lived at that time, went to Greece to Hercules  to help in the fight against the tyrant. Arriving in Britain, they met Morrigan  and the three of them went to meet Arthur. On the way, it turned out that Merlin is a young wizard who has not yet revealed his gift. They managed to change Arthur and make him good, and the evil sorceress Mab died from the giant monster she created.

Appearances
Once Upon a Future King