Snow (Ginnifer Goodwin) is now evil, Regina (Lana Parrilla) is now pure and everything has been turned upside down on ABC's Once Upon a Time.

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With the Author (Patrick Fischler) having the ability to give certain people happy endings, everything has changed in the season 4 finale. ABC released a sneak peek of the finale episode, which features Snow and Regina having huge role reversals.

Snow is reveling in her evilness while Regina essentially begs for mercy. The clip features Snow getting out of a carriage and confronting Regina.

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"I've waited so long for this moment," Snow tells Regina. "Your head is going to look lovely in my trophy room."

"Please Snow, how many times do I have to say I'm sorry?" Regina pleads.

"Once more, from your grave," Snow says with delicious evilness.

"I didn't know what would happen to James I was a child, I was only trying to help you," Regina says.

"You broke a promise. Because of your poor, poor judgment my true love is dead," Snow replies.

This is interesting that in this particular timeline, it looks like Charming's (Josh Dallas) brother James is Snow's true love.

When Charming tells Snow she should "ask her about the boy," Snow does so.

"When does this end, Snow, this blood feud, when does it stop?" Regina cries.

"When i've killed you and every one of your followers," Snow replies.

It is then that Regina goes into a speech about holding hatred and evil in your heart and how it ultimately weighs you down, a telling message considering what we know from her.

"You lost one happy ending and I'm sorry for that but all this killing will only bring more hatred into your life and all you'll be left with is a hole in your heart," Regina says, "and no hope of ever finding true happiness."

"You know nothing of my happiness," Snow says bitterly.

Snow then launches a fireball at Regina, but the clip naturally cuts off after this. It will be interesting to see the full extent of evil Snow and good Regina in the finale.

Once Upon a Time airs Sundays at 8 p.m. ET/PT on ABC.

Watch the sneak peek below: