Jared Padalecki Jared Padalecki

Supernatural's war in Heaven is upon us as the series airs its two-part finale on Friday (8/7c on The CW), and showrunner Sera Gamble promises some deaths, Sam's long-awaited breakdown and "a lot of Castiel" in both episodes.

Gamble wrote the night's first episode, "Let It Bleed," which introduces a new player — at least historically — into the series. Apparently, the late, real-life horror writer H.P. Lovecraft is somehow mixed up in the Winchesters' battle to keep Purgatory at bay. Anyone familiar with his Chthulu mythos will recognize that his terrifying creations fit right in with the Supernatural world.

Supernatural: Castiel bends time and truth

In the second episode, "The Man Who Knew Too Much," we see the culmination of what's going on with Castiel and his season-long quest to oppose Raphael.

Check out what Gamble has to say about Season 6's finale event:

What can you tease about the episode you wrote, "Let It Bleed"?
Sera Gamble: One of the big arcs we played this season for Dean, when we had first seen Dean (Jensen Ackles) this season, he had been retired for an entire year and was living with Lisa and Ben. He left them to resume hunting and be with Sam. While we're glad he did that because we want to watch him on the show and this in many ways is clearly the right choice for everyone, I think there's a part that he left behind with them. More to the point, just having been in their lives put them in danger. He has had this fear that something bad might happen to them. In Episode 21, basically long-story-short, that comes to pass. They are unexpectedly taken and he has to deal with that. He has to deal with the repercussions of having been in their lives. It's basically Dean's worst nightmare.

How does this part pair with the second half of the finale, "The Man Who Knew Too Much"?
Gamble: We have so many mythologies going on that when we heard that we were going to air Episode 21 and 22 on the same night, we talked about breaking it as one huge, two-hour episode with a short cliff-hanger in the middle, but what ended up happening was two distinct episodes. Episode 21 deals with a lot of Dean stuff, and Episode 22 deals with a lot of Sam (Jared Padalecki) stuff. That's just the way it worked out. Both guys are very active in both episodes. There's a lot of Dean in Episode 22 and there's a lot of Sam in Episode 21. And there's a lot of Bobby (Jim Beaver), a lot of Castiel (Mischa Collins) in both. But it kind of ended up being Dean-heavy in 21 and Sam-heavy in 22.

Check out a clip from each episode of the finale event:

What is the Sam-heavy episode going to deal with?
Gamble: This season we structured it with a lot of mysteries and twists and turns, it's kind of like this noir-style thing, so there's like a couple of big bombshells. Here's something definite I can say about Episode 22 that's probably helpful. When Sam got his soul back, Death put this wall up in his mind. Behind the wall are all of his memories of hell, which are incredibly dangerous to him. We know that that wall could crack, and we know that that wall could break. We've been kind of threatening this all season. So Episode 22 deals with that, his amnesia, the wall breaking. We promised it all season.

What can we expect from Castiel now that he's on his own without the Winchesters?
Gamble: The war in heaven becomes a more urgent, heavy thing for Castiel. That will come to the fore at the end of the season. You'll see Castiel and Raphael face off as well. We have a lot to juggle.

TV Guide Magazine exclusive video: Behind the scenes with the Supernatural stars

In an interview, director Robert Singer had hinted that "everyone is not what they appear." What kind of surprises can we expect along those lines?
Gamble: I think hopefully if we've done our job right, there will be a couple of gasps in the last few episodes. Not everyone is who they appear to be on the surface. But it's not like anyone's going to rip their face off and be somebody else underneath though. We're really not that show. In certain ways we've always told those kinds of stories. We always have a thread of darkness and Sam and Dean worrying who they can trust. Their world has always been shaky in that way. We've derived a lot of interesting and kind of fun stories in a dark way because of that.

It wouldn't be a Supernatural finale without some casualties ...
Gamble: We definitely kill people. Characters will be killed and transformed. It's safe to say that characters that people like will be killed. I find that usually when we kill somebody there's a certain amount of blowback because they're always characters that people likes. I usually don't get thank-you notes for the people that we kill. But we have that small group of characters that we go back to because they're precious. The reason we go back to them again and again and again is because they were cool.

Is there a possibility of seeing John Winchester (Jeffrey Dean Morgan) in these last episodes?
Gamble: You won't see John Winchester in Season 6, I'm sorry;. There's always a chance we'll bring him back at some point in show. It's a combination of the right story and Jeffrey Dean being available at that time because he's a busy and popular actor, which we're super-happy about for him.

Who do you think will die in the finale?

Check out a promo for the finale event: