Barbara Hershey and Lana Parilla

If you thought the Evil Queen — who trapped the characters of fairy tale land in the real world in order to get vengeance on Snow White — was bad, just wait until you meet her mother.

This Sunday's episode of Once Upon a Time will introduce Regina's (Lana Parrilla) more evil mom, Cora (Barbara Hershey), who will help to shine some light on how a young and innocent girl came to be the Evil Queen. The hour will also feature what made the Evil Queen hate Snow (Ginnifer Goodwin) — and it might cause from some fans to turn Team Regina!

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"I think they'll feel sympathetic toward Regina," Hershey says. "Lana had the chance, which was great, of playing the Evil Queen before she was a queen and before she was evil. You could see the innocence before it all happened. You get to find out why she hates Snow White so much and why she became evil." 

Regina's overbearing mother had very high expectations of her. "She is evil, she is consumed by evil and can wield magic brilliantly, so the stakes are much higher," Hershey says. "She wants her daughter to make the right choices. She has ambition for her and doesn't want her to marry the stable boy. She wants her to marry the King."

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Still, even Cora could not have predicted just how evil Regina would become -- which is not to say she wouldn't be happy about her daughter unleashing the curse to end all curses. "She probably would be proud of her power and of her being able to create such an effect," Hershey says. "She probably wouldn't read it as evil."

Should Once get renewed, the producers have the option to bring Hershey back for additional episodes, but since we're meeting Cora so late in the season, it begs the question: what happened to the Evil Queen's mother in the first place? Did she perish before the curse was enacted? Will she make her way to Storybrooke? "They've left it very open-ended and I'm open," Hershey says.

Check out a sneak peek of Cora and Regina's relationship in this clip from Sunday's episode of Once Upon a Time, airing 8/7c on ABC.