[This story contains spoilers for season nine, episode 15 of AMC's The Walking Dead, "The Calm Before," and the comics on which the series is based.]

Winter is coming — and not just to Game of Thrones. Hot on the heels of losing Henry (Matt Lintz), Tara (Alanna Masterson) and Enid (Katelyn Nacon) in one of the deadliest acts of violence ever committed on The Walking Dead, the world of the walkers is about to get painted with a coat of white to go with its signature red, all thanks to a stormy season nine finale.

"The Storm," airing March 31, stands ready to fulfill one of the ancient promises from Robert Kirkman and Charlie Adlard's comic book source material: winter in the south, as featured prominently in an early run of the comics. Snow finally falls in the season nine finale, and as co-executive producer and director Greg Nicotero tells The Hollywood Reporter, "It feels unlike any other episode we have ever produced."

Next week's season nine finale poses many challenges, winter conditions aside. It's forced to respond to the call of the season's penultimate episode, which ended Sunday with one of the most highly anticipated moments from the comics, finally realized in brutal fashion. In the original telling of the tale (spoilers ahead from the comics), Ezekiel (Khary Payton) and Rosita (Christian Serratos) wound up with their severed heads on spikes. In the AMC adaptation, their lives are spared, but at the expense of two other series regulars in the form of Masterson and Nacon, not to mention a legacy castmember in the form of Lintz, whose siblings Madison and Macsen both previously appeared as Sophia and Young Henry, respectively. (Click here to read how it all went down.)

How did the brutal deaths come together from Nicotero's side of the border, as the man responsible for creating the series' iconic horror effects? Read on for his thoughts on the subject, plus his tease of what to expect in the snowy season finale.

When we spoke about the Whisperers, you described seeing them in the comics for the first time as an indelible image. Certainly, the heads on spikes ranks right up there as far as indelible impact.

Absolutely. It's funny … we talked about when Lori (Sarah Wayne Callies) got killed, too, and this is definitely one of them. When we break the story, and when the writers are in the writers room, we don't always know when an event is coming. A lot of times, we'll find out at the very beginning of the season where some of the landmarks are. But we had no idea who it was going to be or when it was going to be until probably two or three episodes before we shot.

Gene Page/AMC

Which speaks to the tragedy of the act. The characters who die aren't selected by Alpha (Samantha Morton) for specific, personal reasons. There's a randomness to their deaths.

I think that's what's so tragic about it. First of all, the deaths are at the hands of a human being instead of walkers, so that immediately makes it different. In a world where you struggle to survive in this upside-down world of the undead, you figure, "OK, that's how I'm going to go." But with the introduction of the Governor (David Morrissey), Negan (Jeffrey Dean Morgan) and then the Whisperers, you're constantly reminded that man's inhumanity toward man is the most horrific thing that can occur. There's a real brutality to it. I loved in the script how Siddiq (Avi Nash) talks about how the [victims] all fought until the end. There was no fear. They were willing to band together and fight for each other in unsurmountable, unbeatable odds. There's a randomness to it. That's part of what makes it so tragic. It has that Glenn (Steven Yeun) feel, where it's random and uncontrollable. You don't expect it. You don't see it coming. And then you get this one-two punch.

What went into selecting the ultimate victims, especially the main victims: Henry, Tara and Enid?

There's so much behind the decisions of who goes and who doesn't go. Even at the beginning of the season, when we knew the sequence was coming, everybody was always saying to Christian and Khary: "Heads on spikes are coming! Here it comes!" But it's always about what these moments and these deaths do to other characters that catapults them forward. In regard to Henry and his relationship to Carol (Melissa McBride), Daryl (Norman Reedus) and Ezekiel … there's a very specific reason to lose him. In terms of other characters? Tara stepped up as a leader once Jesus (Tom Payne) died. She was showing some real authority and leadership at Hilltop. Ultimately, it's an organic decision, the way it evolves, like the relationship between Enid and Alden (Callan McAuliffe). You see a budding relationship and a budding romance, where people are rising to what makes them the best person they can be, like Tara. In many instances, some people find those realizations. In other instances, it's brutally torn from them.

Charlie Adlard/Image Comics/Skybound

What was the process for creating the heads on spikes?

The big challenge was creating nine heads in about two weeks. We didn't have a tremendous amount of time to actually do that. We did head casts of most of the actors, and then for a few of them — for Katelyn, Alanna and Matt — we did animatronic heads with full radio control movement and function. When they came upon the heads, they see the first few, which are non-articulated. The idea was to put a little bit of digital movement in the mouths. When we get to the three who are the three biggest characters, I wanted to come up with something that gave the actors something to perform against. What we did was very similar to what we did with Hershel [in season four]. We put some digital face replacement on the animatronic heads, so that we put real eyes on the fake heads. That mixture of real and digital always allows for the best effects. Our visual effects team did a really great job putting those elements onto the animatronic heads. We used every single trick in the book to pull that off.

How does an event like this compare to the destruction of the prison and the arrival of Negan?

I think there are landmarks in the show that change the direction of characters. I think this is one of them. It's something Kirkman wrote so brilliantly and so beautifully, the idea that there's this divide, and Alpha has said: "You can exist there. We exist here. If you cross our border, you're in trouble." The fact that she makes this statement, and makes a border that's lined with the heads of their own people? It's such a brilliant notion. Without a doubt, it has a very iconic and epic feel to it. Samantha has done such an amazing job this season. She so embodies everything that the show needs and wants. Just to know how there's no coming back from this … it's pretty astounding.

The episode ends with snow falling. Are we finally getting full-blown winter on The Walking Dead, as we saw in the early issues of the comics?

Yes, we are. We finally have our frozen zombies. We finally have our winter episode.

I'm so excited.

Me too! (Laughs.) I'm dying for people to see it. For me, it was one of the most technically challenging things I have ever done in my career as a director and as an effects artist who has to visualize this world. The other big challenge is this: How do you follow something like episode 15 with a season finale? While we were shooting it, we all said that episode 15 felt like a season finale. It was a moment where you want to end the show with people reeling and recovering. Adding a little P.S. on it, with the magnitude of what we did? I think people are going to be blown away.

How are you going to follow it, then? Winter, of course, but what about emotionally?

The nice thing about our season premieres and our season finales are setting the table for the seasons to come and the seasons to follow. There's a lot of good emotion and stories that are wrapped up with some character development and arcs. There are other stories we're setting up. It has a lot of mood to it. It has a lot of style to it. It feels unlike any other episode we have ever produced. In that way, I think we're going to have our audience saying, "Man, they keep giving us more and more stuff that makes us want to stay tuned. It makes us want to know what's going to happen next." As soon as I was told we were going to do snow? I was like, "Wow. It's Georgia. How do we do snow in Georgia?" We'll talk about the answer after you see the episode.

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