[This story contains spoilers from Sunday's musical episode of ABC's Once Upon a Time.]

Now that Once Upon a Time has completed its musical wedding extravaganza, it’s time for what Josh Dallas calls “a showdown of epic proportions.”

The Black Fairy’s (Jaime Murray) curse hit Storybrooke just as Emma (Jennifer Morrison) and Hook (Colin O’Donoghue) completed their vows and enjoyed a brief moment of celebration. Now, it’s impossible to say to where they've been transported and what will happen, but one thing is for sure: It's time for that epic Final Battle to begin.

To hear showrunners Adam Horowitz and Eddy Kitsis tell it, there's a pretty huge battle right out of the gate as the two-hour finale kicks off.

“There's a curse that's coming,” Horowitz told press, including The Hollywood Reporter, following a recent screening. “We're well aware that we've done a curse occasionally in the past on the show, but this time we're trying to do a little twist on it.”

“I would say that the Final Battle and the curse are all tied in one,” Kitsis adds, “And the first act of the finale will make sense of what we're doing this time.”

“It's a combo platter kind of curse. There's a bunch of different things that happen,” says Horowitz.

So far, The Black Fairy hasn’t given any hint of what her curse will do or where it could take the residents of Storybrooke. Even worse, there’s not a single clue to be found about how to break this particular curse. Given that it’s the Final Battle that’s been building for six seasons, true love’s kiss probably won’t be enough to crack this one.

Luckily, Ginnifer Goodwin was willing to provide some insight into how the Charming family will tackle this new conundrum. “The breaking of the curse involves something far more dramatic than anything that’s broken a curse before,” Goodwin says. “What broke the very first season’s curse was the kiss and a very pure, unromantic true love expressed between mother and son. And the love that it takes in the finale to do what has to be done to break the curse, I feel it’s categorically bigger.”

This finale will undoubtedly be different from any others because for the first time, Once Upon a Time is heading into its final episode on the bubble as the drama awaits word on its future. That fact played heavily on the decision-making process for this episode, and Kitsis and Horowitz were aware that they needed to write a season finale that could also function as a series finale if need be.

“We understand that this could be the last year,” Kitsis says. “So we aren’t trying to hope for the best. We feel like we’ve completed this story, and the next chapter of Once Upon a Time will be completely different.”

“The way we sort of look at it is, these are stories for these characters, and there are set endpoints to different stories,” says Horowitz, “But that doesn’t mean there aren’t new stories for different characters. I think that by the end of the season finale, a lot of what we’ve been doing for the last six years is wrapped up — we hope in a very satisfying way — and then we move forward in a way that at the end of it, hopefully you’ll see what we’re hoping to do in season seven.”

If the show does return for another year, it’s growing increasingly clear that a few characters may not be coming along for the ride. Kitsis confirmed as much, saying, “Creatively it’s time to end a few stories. ... We feel like this is the kind of show that regenerates, and I think when you see the ending you’ll go, ‘Oh, yeah.’”

The best bet for characters likely to be written out would be Charming and Snow, seeing as their story has truly come full circle. The pilot began with the daunting promise that Emma would be the Savior and return to save them all during the Final Battle. Now that the Final Battle is bound to happen, it would make that circle (and that chapter of their story) complete, allowing for Snow and Charming to finally just relax into royal retirement.

If it is the end for them, Goodwin and Dallas have both said that they’re satisfied with the way the finale shakes out for their characters — and the show as a whole.

“I think they’ve honored these characters and this part of the story, part of their journey, and I think each character gets something that the fans should be happy with that each character deserves,” Dallas says. “If it’s the last episode, I would be satisfied.”

It’s true that at this point in time, most characters have their stories pretty well wrapped up if you don’t take into account the Black Fairy’s curse. Emma has her happy ending with Hook, Snow and Charming are both awake and reunited with their family, and Regina (Lana Parrilla) has finally managed to make amends with Zelena (Rebecca Mader). Only Rumple and Belle and their ever-shifting relationship status (plus the fate of their son, Gideon) is still up for grabs. 

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