Once Upon a Time dropped a couple casting bombshells at Comic-Con in San Diego this week:

FIRST, British actor Elliot Knight has been cast in the pivotal, recurring Season 5 role of Merlin.

The iconic sorcerer was referenced toward the end of Season 4 as the only person who holds the key to eliminating the Darkness from the world for good, thereby saving Emma from her dangerous new fate.

SECOND, Deadline confirms that Portuguese actress Joana Metrass has nabbed the recurring role of Guinevere, the queen to King Arthur (an already-cast Liam Garrigan).

As previously reported, Sinqua Walls will return in some capacity this fall as Lancelot, as the entire Camelot crew will play a key role on Once Upon a Time Season 5.

Along those lines, Wayward Pines mailman Andrew Jenkins will guest star as  Percival, one of Arthur’s most dedicated knights.

Once Upon a Time Season 5 will premiere on Sunday, September 27.

Once Upon a Time Season 5: What We Know So Far

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Matt Richenthal is the Editor in Chief of TV Fanatic. Follow him on Twitter and on Google+.