Regina (Lana Parrilla) will play a key role in helping lost souls in the Underworld in upcoming episodes of ABC's Once Upon a Time.

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Regina is set to help souls in the Underworld with their unfinished business. Parrilla explained in a new Hollywood Reporter article about how her character will step up in the episodes to come.

"Because Regina is now a hero and has joined the hero pack, she feels obligated to help these souls. ... It's giving everyone the opportunity to make amends with their past and help these souls move on," Parrilla said. "And that's the hero in all these characters. We're not just down there to help one person - we end up going down there to help many."

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The best example of unfinished business, of course, is Regina's relationship with her mother, Cora (Barbara Hershey). Regina will reunite with Cora in the Underworld and gradually learn that the reason she is trapped there is due to unfinished business between them.

"When she sees her mom for the first time, it's a happy reunion, but it's bittersweet," Parrilla said. "We start to learn why Cora's trapped down there, and we learn that Cora's there because Regina is part of her unfinished business."

This theme of unfinished business will be prevalent in the second half of the season, with many characters having to grapple with their pasts.

Once Upon a Time returns for the second half of season 5 on Sunday at 8 p.m. ET/PT on ABC.

Tags: Once Upon A Time television ABC