Much of the speculation going into Season 4 of ABC's Once Upon a Time has been around Elizabeth Mitchell's mystery character, and new photos of the actress on the set have now been revealed.

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Mitchell was photographed wearing a very sparkly gown on the set of the ABC fantasy series, adding to speculation that she could be playing The Snow Queen in Season 4. Showrunners Edward Kitsis and Adam Horowitz were previously asked if Mitchell would be playing The Snow Queen or Elsa (Georgina Haig) and Anna's (Elizabeth Lail) mother, and they confirmed that it would be one of those two.

Based on Mitchell's elegant outfit, it could go either way, but it seems more likely for The Snow Queen to wear such royal clothing.

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The showrunners also spoke with TVLine recently about Mitchell's character, where they teased a few more details.

"She's awesome, we love her, we're so happy to have her and we can't wait for the audience to discover who she is playing," Horowitz said. Asked if she could be playing someone evil, Kitsis quipped, "We never bring Lost actors on our show to be villains, so...."

This is obviously sarcasm, considering Lost alum Rebecca Mader just finished her guest arc as the Wicked Witch in the second half of Season 3.

Mitchell previously starred on ABC's mysterious island drama Lost where she played Juliette.

It is currently unknown how often Mitchell will be appearing in the fourth season of Once Upon a Time.

The series is set to premiere its fourth season Sunday, Sept. 28 at 8 p.m. ET/PT on ABC.

Tags: Once Upon A Time television ABC