Misha Collins Misha Collins

On Supernatural's upcoming Western-themed episode, Dean and Sam aren't the only ones facing a life or death showdown.

After Castiel (Misha Collins) sends the Winchesters (Jensen Ackles, Jared Padalecki) back in time to follow up on a clue from Samuel Colt's diary, he continues with his own efforts to build up a supernatural army. As the season has been progressing, however, more and more of his actions have become suspect.

In a surprising confrontation, we see Castiel engage in a battle to defend his hidden agenda. In the aftermath, he goes back to Bobby and the boys with a slightly skewed account of the tussle.

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"He doesn't exactly tell the whole story to them," executive producer Sera Gamble tells TVGuide.com. "Cas' role has changed in that he's not just a soldier anymore, he is responsible for a lot of people. One of the difficult lessons that Cas has been forced to learn is that with great responsibility comes compromise, a really difficult compromise. He's commanding essentially a guerrilla army and like all commanders and, in a certain way like all politicians, you might find yourself bending the truth at one time or another."

The show's writers deliberately decided to tarnish Castiel this season in order to test his character.

"That's something we were interested in exploring for Castiel who is such a sincere and honest, really deeply feeling character on the show," Gamble says. "Angels have been just d---s on the show, but Castiel has been the opposite, so we put him in this position where he'd be forced to have to do these things that he doesn't want to have to do necessarily."

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And for the comic book readers out there, keep an eye out for what Gamble says just might be a nod to a Marvel character, although it's one she didn't catch at first.

"I wouldn't put it past [writers Dan Loflin and Andrew Dabb]," she says. "Especially Andrew reads a lot of comic books so it's totally possible. I didn't even notice!"

Supernatural airs on Fridays at 9/8c on the CW. Check out what else Gamble has to say about "Frontierland."