Once Upon a Time's penultimate episode was a bit of a doozy, but what else do you expect when the darkest version of Rumplestiltskin (Robert Carlyle) shows up to finally make good on an old prophecy?

According to executive producers Adam Horowitz and Eddy Kitsis, his villainy has only just begun!

"He was one of the greatest villains, if not the greatest, on the show," Kitsis says of the decision to bring Rumple back as the final boss, so to speak. "For us, we just kind of selfishly wanted to write him and see it one more time. I think you'll see in the finale that a lot of people have to face themselves as the villain."

"The show needed to, in our mind, go back to its roots for the ending," Horowitz adds. "It had to kind of come full circle, so bringing Rumple back as a villain felt just right to us."

Wish Realm Rumple kicked off the night with a flashback to an offer he made teenage Henry (Jared Gilmore) in the Enchanted Forest. Poor Henry just couldn't manage to snag his fairytale ending, and Rumple offered to help make all his dreams come true. Henry, being wise to Rumple's wicked ways, obviously turned down the offer, but Rumple maintained that one day he'd change his mind.

Fast forward 15 years or so, and Rumple turned out to be right — just not in the way we ever expected.

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After kidnapping a newly un-cursed Lucy (Alison Fernandez) and Ella (Dania Ramirez), Wish Realm Rumple commanded Henry to steal real Rumple's dagger and hand it over. That led to Henry (Andrew J. West), Hook (Colin O'Donoghue), real Rumple and Regina (Lana Parrilla) embarking on a rescue mission to the Wish Realm, where Henry ended up picking the Author's Pen back up in an attempt to save his family.

(Cue a hilarious joke about the confusing timelines of this show.)

When push came to shove though, what Rumple really wanted wasn't the dagger at all: he wanted the Author's Pen in order to subvert the prophecy made in Season 2 about Henry being Rumple's "undoing." Not to mention, that flashback was not technically a flashback at all; Wish Realm Rumple revealed he made that offer to Wish Realm Henry, who eventually took him up on it. Now armed with the Author's Pen and a whole lot of rage about unfulfilled happy endings, Wish Realm Henry could end up being everyone's undoing.

Luckily, Robin (Tiera Skovbye) and Alice (Rose Reynolds) found a magic bean that would allow them to travel to the Wish Realm to help, but first they had to stop by Storybrooke to pick up a few allies. With a whole bunch of original Once Upon a Time characters at their backs, there's no way real Rumple can lose this fight... right?

Once Upon a Time's series finale airs Friday, May 18 at 8/7c on ABC.

Robert Carlyle, <em>Once Upon a Time</em>Robert Carlyle, Once Upon a Time