There have been several incarnations of various fairy tale characters involved in the highly popular ABC series "Once Upon a Time." That will also be the case in Season 5 when the show takes on the "King Arthur" and "Merlin" stories to place them in the series with the rest of the existing cast of characters, according to Deadline.

This also includes the parts of Guinevere, who will be played by actress Joana Metrass, and the sorcerer Merlin, who will be played by Elliot Knight. They will both be joining Ginnifer Goodwin's Mary Blanchard (Snow White) and Jennifer Morrison's Emma Swan on the show for another season of twisted tales based on the legendary original stories.

The additional cast member joining the show as King Arthur's most loyal knight Percival will be Andrew Jenkins.

In Season 5, the story will focus on Emma Swan's transition from Savior to Dark One, which has been a theme that was breaking in previous seasons. The season will play out with the search for Merlin, who they believe can rescue Emma from her fate and bring her back to the powers of the light. But bringing Emma back to the Savior could call for drastic measures, and sometimes, those are more than a sorcerer can handle.

News of theses additional cast announcements comes ahead of the San Diego Comic Con event. The party that ABC hosted last year made quite an impression when they announced the casting for the upcoming "Frozen" tie-in.

Metrass will also be working with Guy Ritchie on the upcoming remake of "The Man From U.N.C.L.E." in the U.K.

Fans might recall Jenkins from the AMC hit "The Killing" as a recurring character. He is also a recurring character on Fox's "Wayward Pines."

Knight starred in the 2012 Syfy series "Sinbad" and portrayed a recurring character in ABC's "How To Get Away With Murder."