Pack your suitcases for Oz, Once Upon a Time fans, because we’re finally going to get to see where the Wicked Witch came from. In Season 3, Episode 16 (“It’s Not Easy Being Green”), we’ll get flashbacks to the fabled land and an epic showdown between Zelena (Rebecca Mader) and Regina (Lana Parrilla) in the streets of Storybrooke.

We already know that Zelena and Regina are half-sisters, but given the fact that this news was dished out in the forgotten year, it’s all about to rise to the surface once more when the ladies battle to the death.

And if you’re wondering if the Wicked Witch still has control over Rumple (Robert Carlyle), the answer is a resounding yes. In fact, we’ll find out that Greenie has had her eye on the Dark One ever since she was in Oz. Could they be related?

Check out the full synopsis for the April 6 episode here:

“With Rumplestiltskin as her slave, Zelena challenges Regina to a fight to the death and shocks the Evil Queen with the reveal of their familial connection, and the town lays Neal to rest. Meanwhile, back in the past in the land of Oz, a jealous Zelena asks the Wizard to send her to Fairy Tale Land after discovering that she has a sister, Regina, and that Rumplestiltskin is training her to become a powerful force to be reckoned with.”

We’re excited to see the epic showdown between Regina and Zelena. Can she overcome the Wicked Witch?

Once Upon a Time airs Sunday nights at 8 p.m. ET on ABC.
Carson Blackwelder is an Assistant Editor at Wetpaint Entertainment. Follow him on Twitter and Google+!