New Once Upon a Time series regulars Rebecca Mader and Sean Maguire recently spoke about the significance of their roles in season 5.

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Maguire, who plays Robin Hood, and Mader, who plays Zelena, spoke at Comic-Con last month and in a new video posted this week from BuddyTV, they talked about their characters' motivations.

While Zelena is set to have Robin's baby, it isn't her primary goal to do so.

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"I think the story is about destroying Regina's happiness," Mader says. Ultimately, she was intent on taking away her sister's true love.

"Whether she'll be a good mom or not, I don't know. Hopefully it will change her in a positive way," Mader adds.

Meanwhile, Maguire is unaware of how Robin will respond to having a baby. Though he said there's a line from Regina (Lana Parrilla) in the season 5 premiere that is "quite telling about where [they're] going."

As for the other major storyline, Emma (Jennifer Morrison) succumbing to the dark side, Mader says it's set to be "really upsetting and heartbreaking for everybody" when Emma turns dark. "It's going to be saving the savior in a way from herself, from the darkness."

Maguire considers this season to be "our dark chapter," likening it to The Empire Strikes Back.

Once Upon a Time season 5 premieres Sunday, Sept. 27 at 8 p.m. ET/PT on ABC.

Tags: Once Upon A Time television ABC