Jensen Ackles and Jared Padalecki

The Grim Reaper is hitting Supernatural again.

As Sam (Jared Padalecki) and Dean (Jensen Ackles) prepare to take on Eve, aka the Mother of All (Julia Maxwell), executive producer Sera Gamble told TVGuide.com at Sunday's PaleyFest that the season finale will feature at least two unexpected deaths.

"There will definitely be deaths," said Gamble, who penned the penultimate episode for Season 6. "I would say that the last couple of episodes are pretty dark. The situation is rather desperate for Sam and Dean and they truly have to ban together to get the job done."

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Executive producer Eric Kripke, who just finished writing the season finale, said there will be a face-to-face confrontation between the brothers and Eve. "It's epic and daunting," Misha Collins, who plays Castiel, added. "The final confrontation is definitely not what anyone is expecting. It is, however, larger and more epic than the viewers are expecting."

But you might not want to hold your breath for a resolution. Despite Supernatural not being renewed for a seventh season — yet! — the producers are leaving the finale wide open. "It's a cliffhanger, so everyone needs to be prepared that they're going to be tearing their hair out all summer," Kripke says. 

"We're certainly preparing for a Season 7," Gamble says, adding that if there isn't one, the cliffhanger might anger fans.

"This is a cliffhanger unlike any other," Padalecki says. "We've had Sam die and Dean die and dad die, so we've had a lot of deaths. This one doesn't necessarily end with death, but with a whole new beginning."

On top of the impending battle with the Mother of All, Season 6 has seen Sam plagued with a memory block, placed on him by Death, which has kept him from learning the truth of what happened during his year without a soul. "I will say we conclusively deal with Sam's amnesia and the fact that he doesn't remember what happened to him in hell," Kripke says." He's got this bit of drywall in his head, but it's a shabby, unstable piece of drywall and it's only a matter of time before the wall falls down, and in the finale, the wall falls down."

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"It's something that Sam is both afraid of and also he's dying to know what he did that year that he was soulless," Gamble adds. "It's something that Dean has great fear about. Every ounce of big-brother protectiveness inside him wants to shield Sam from what might happen if the wall comes down, so it's a pretty major thing for them."

The truth, however daunting it may be, will not tear apart the brothers. "We're actually enjoying that, for the first time in a long time, the brothers are a really strong, cohesive unit, so we're going to keep them like that for the foreseeable future," Kripke says.

Supernatural airs Fridays at 9/8c on the CW.