Game of Thrones is a perennial favorite at the Emmys, having raked in 63 wins over the past seasons. But it has absolutely dominated in the realm of visual effects, having won for the past three years straight. We talked with VFX supervisor Joe Bauer and prosthetics supervisor Barrie Gower (both hold Emmys for the show) about the epic battle of Hardhome and how they set a record for the number of people set on fire in a day.

Every year, Thrones has presented an amazing, season-defining episode and this season it was the battle of Hardhome. It was referenced, but never seen in the books, so even jaded fans of A Song of Ice and Fire had something to cheer about. The team had some experience with multiple zombies — Episode 10 of the fourth season features a climactic fight — but it was “on a much lower scale,” says Gower.

The battle revolves around the White Walkers and their zombie hordes, known as wights. Gower says the wights were broken down into three different categories: the “super fresh,” recently revived corpses who were mainly handled by makeup designer Jane Walker; “mid-decomposition,” who had prosthetics for the “fleshy bits hanging off, cavities here and there”; and the green screen wights, whose missing limbs and empty skulls where a combination of prosthetics and digital effects, which removed green leotards and heads covered in paint. There was even a wight (the one whose head is crushed as he claws his way under the gate) who was alternately a stunt performer and a puppeteer. The head was made of foam so “the actor could stamp on it as many times as he wanted, basically.”

“On any given day [the shoot for the battle ran for some two weeks], we had about 80 zombies,” says Gower. The prosthetics and makeup crew would begin showing up at 2:15 a.m. so they would be ready to shoot by sun-up. Gower’s favorite creatures include:

One of the Others they nicknamed “White Walker X” (played by Vladimir Furdick). He’s the one who was shattered by Jon Snow’s Valyrian steel sword.

Wun Wun the giant. They “made a huge foam suit which he fits into and then the costume department wrapped him with animal pelts, all kinds of bones and things. He had quite an extensive silicone rubber prosthetic makeup on his head.” Gower is also “a big fan of the hands. That was a joy to do.” Wun Wun (played by the 7'1” Ian Whyte) was actually shot separately on a green screen stage in Belfast.

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The lead child wight. “We covered him in full facial appliances — a few pieces on his body — and we put green screen patches for his eyes and chunks on his body.” Visual effects removed the chunks, and reduced his body, giving him the skeletal look. “On the day we were really pleased with the result,” says Gower, “but we knew visual effects would take it to another level.”

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Another hugely collaborative part of the Hardhome battle once again involved the giant. In addition to the fully computer generated wights that clung to him, “Wun Wun the giant comes smashing out of the longhall and that had to be done over a couple of days,” says Bauer. “The special effects team led by Stuart Brisdon had to create a rig that would both annihilate a pretty big corner of this big log structure and then disappear so it didn’t block anything.” That was then combined with the miniature version and the green screened actor. “Everything just fit together perfectly. When you’re working with the right people, it certainly is a lot of fun.”

Although “about 80 percent of our work was for the Hardhome episode,” says Gower, there was still plenty to be done the rest of the season. For the gladiatorial scenes in Mereen, they sent Stuart Bray and David Brown out with “this kit, basically, of rubber bits and pieces,” to accommodate whatever was needed. “'We’ll have two, three throat cuts tomorrow,'” says Gower, recalling the shoot with an offhanded cheerfulness. “'This guy’s going to have his head caved in and then we’ve got decapitations on this day and blah blah blah.’ It was a really fun time for our two guys!” he says with a laugh, fully aware of how strange his words would sound out of context.

For the visual effects team, the highlight of their season has been the Drogon scene from Episode 9, “The Dance of Dragons.” Although they had done a fire effect previously, VFX supervisor Bauer says the now enormous dragon required a completely different approach.

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“In Season 3, the dragon was quite small, so as he flapped, he pretty much stayed in one place.” But now that he’s sixty feet, wingtip to wingtip, the team decided to pre-animate Drogon and program his movements into a motion control rig holding a fifty-foot flamethrower. It was such a big fire stunt that, “We [accidentally] set the record that had been previously held by Braveheart by burning 21 people in one day. It wasn’t our goal; it just happened to be the case.” They only had time to do it once and, despite the time constraints, they managed to get it done with no more than “one small blister on a pinkie,” worth of injuries.

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For the shots where Danaerys has to climb on Drogon, the special effects department built a full-size “buck” attached to a hydraulic rig. The rest are composed of 3D models which have to be changed year-by-year as the dragons keep growing. While occasionally creators Dan Weiss and David Benioff will offer input — Bauer recalls Weiss acting out the beats of Drogon crawling down the side of Danaerys’s pyramid — for the most part, he says, “We all seem to be seeing things in the same way.”

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While Bauer’s team is generally recognized for their large set pieces, they also have a hand in even the tiniest details. The battle for the Wall at the end of Season 4, for example, was shot during rains that alternated between a sprinkle and a downpour. “The most difficult and un-glorious work is painting every drop of rain out so you don’t have a continuity problem.”

The next season will be even more impressive and complex. “Between Season 3 and Season 5, our shot count doubled,” explains Bauer. There will be “other environments that we haven’t seen people in before.” Not only that, “The dragons will again be double in size.” Which isn’t a problem for the graphics, but on set it’s an issue. “When the dragons were small, we had little foam rubber models of each dragon and we could carry them on and off of the set and it was no big deal. Last year, the best we could do was a head and this year it’s going to be a finger nail or something, I’m not really sure.”

Related: 'Game of Thrones’ Season 5 Finale: What We Expect to See, What We Hope to See, and What We Know We Won’t See

Gower was much more cryptic about a mind-blowing VFX challenge that fans will see in Season 6… probably. “Benioff and Weiss, when they write the outline each year, for last two years, we got to this one point and we read this one gag and thought 'Oh my God, how the hell are we going to do that? But this is going to be incredible!’ And then it got pulled and we didn’t do it in Season 4,” says Gower. “And then, lo and behold, in Season 5 there it was again. And it’s pulled again! But now, in Season 6, it looks like we’re going to do it. Fingers crossed they won’t chicken out.”

What could it be? Perhaps he’s referring to the hints that have been lingering for some time now of a character who hasn’t yet been seen from the books… Alas, it’ll be at least another year before we find out for sure.

The season finale of Game of Thrones airs Sunday, June 14 at 9 p.m. on HBO.