The Northman director breaks down the finale's nude volcano brawl

Warning: Spoilers from The Northman, including the ending, are discussed in this article.

Robert Eggers knew two things after his first visit to Iceland: He could see himself maybe one day making a Viking movie, and if it ever became a reality, he would end that Viking movie with a naked sword fight on a volcano. So it came to pass with The Northman.

Alexander Skarsgård stars in The Witch and The Lighthouse director's third film (currently in theaters) as Amleth, a Viking prince out to kill his uncle Fjölnir (Claes Bang) for murdering his father, King Aurvandil (Ethan Hawke). (If the tale sounds familiar, it's because it's based on the Nordic story that inspired William Shakespeare's Hamlet.) Amleth's vengeful odyssey concludes with Eggers' vision brought to life: a mythic stand-off between Amleth and Fjölnir, wielding swords and shields in the nude, on an erupting Mt. Hekla.

Unpacking the making of this fiery climax with EW, Eggers thinks back to that first trip to Iceland. "The landscapes were so epic and brutal and, this seems stupid to say, there was just something so elemental about it," he says.

"Ireland in drag"

People have shot directly on the site of Hekla as it was erupting, and it could've been a possibility for The Northman. But Eggers knew the finale battle had to be contained. So, the filmmaker tapped Ireland to double for Iceland.

Swedish pop singer Björk, one of Eggers' actors, put it best when she came to the spot in Belfast where production designer Craig Lathrop transformed a quarry to look like Hekla. "I said, 'What do you think? Does it look like Iceland?' " Eggers recalls. "She's like, 'Yeah. It's Ireland in drag.' "

If Ireland was a drag queen, then Lathrop, Sam Conway, Jarin Blaschke, Seamus Lynch, and Angela Barson were her makeup artists.

Lathrop brought in black earth to dress the Belfast quarry to look like volcanic ash, plus ground rubber to make the surface easier on the actors' bare feet. Conway, the special effects supervisor, brought in Dantes, devices that shoot massive flames. "They brought in black smoke and gray smoke and tons of falling ash and floating cinders," Eggers notes. "The vast majority of all that stuff that you see in the final fight is practical stuff."

Then Blaschke, the cinematographer; Lynch, the gaffer; and Eggers embedded special LED lights that were programmed to move like lava into the ground. (They were later enhanced in editing to make it look like lava.) For the final touch, Barson, another VFX supervisor, shot documentary footage of the real Hekla erupting in Iceland to make the scene feel as real as possible.

"To be totally frank, I didn't know that this quarry was really going to look good. We were worried that it was not going to look like a volcano," Eggers says. "I remember saying to Sjón, my Icelandic co-writer, 'Is this a stupid American ending?' And he said, 'It could be, but we'll make sure that it's not.' After we did a couple takes, Mark Huffam, one of the producers, came up to me and he was like, 'To be honest, I didn't think it was going to work, but this looks good.' "

G-strings and CGI testicles

Eggers first had to figure out how nudity would work in the context of The Northman. As much as a general audience would take any excuse to see the 6-foot-4 Skarsgård bare his chest, it required research, and the process was more complicated than it seems.

Eggers wanted to be historically accurate but found most of the pertinent sagas about the day-to-day lives of Vikings were written hundreds of years after the fact through a Christian lens. Each piece of intel required further examination.

"I will spare you the onion-peeling. This is what we went with based on the research: Nudity is taboo in the Viking age, and nudity is used in rituals where you're going into liminal states of being," Eggers explains.

Earlier in the film, a young Amleth follows his dad's lead in stripping off his clothes to drink a hallucinatory concoction before a holy man (Willem Dafoe) and howl like a wolf to unleash his inner animal spirit. A later funeral scene involving the burying of Fjölnir's firstborn son, killed by Amleth, sees Fjölnir and the next child in line to succeed his titles nude before the ceremony. These moments gave more credence to the nudity in the finale.

"The berserker warriors, who are bear warriors, and the Ulfheonar, they're wolf warriors — their nudity is scary to people," Eggers says. "Other Vikings wear armor. They are naked to show their ferocity, their invincibility. This naked sword fight is at the gates of hell and is this full circle of this revenge. The duel itself is a ritual and the ferocity of the nudity is, again, this elemental thing that I wanted."

Skarsgård and Bang weren't themselves fully nude, but they were close. They were wearing G-strings, plus some special effects magic. Says Eggers, "We had to put in some CG testicles every now and again to finish the illusion of full nudity."

To the death

Eggers gets pretty candid about his experience on The Northman. "Every day was insanely stressful," he says. "If I had to face the responsibility and pressure that I was under in the mirror, I would've died. So, you just have to not care and just know that you're trying to make the best thing you can possibly do and it's about the story and not about you."

When it came time to the finale, Eggers had the benefit of a group effort: "Everyone knew this is the climax of the film and it needed to be great, so everyone was pushing themselves as hard as they could."

Skarsgård and Bang spent days working with fight choreographer C.C. Smiff and their stunt doubles to instill the battle movements into their muscle memory. It was all based around what historians believe to be elite Viking fighting moves.

Eggers explains, "Viking cross-guards [on swords] are really tiny and it seems to make a whole lot of sense to have much larger cross-guards, but people have been fighting with swords for a long time before the Viking age. Obviously, there must have been a reason why. And it seems they're always fighting with shields. So, there's the theory that perhaps the shields did a lot of the work that a cross-guard would do. There's a lot of using shields as an offensive weapon, as well."

As Smiff developed the movement, Eggers and Blaschke filmed the rehearsals on their cell phones to pin point optimal angles. Come the day of the shoot, camera operator Chris Plevin essentially had "a whole lot of track," as Eggers puts it, plus a camera attached to a crane to capture the entire sequence: Skarsgård's Amleth emerges from the black smoke of the volcano with shield and sword in hand when Fjölnir launches at his nephew, propelling the action across Hekla.

Eggers remembers the intensity between the two actors. "One of the first really great takes that Claes did, I was like, 'Man, your stunt double better watch out, because I haven't seen them do it with that much intensity before,' " he notes of Bang's performance. But the filmmaker will never forget the scream Skarsgård let out towards the end before Amleth decapitates Fjölnir right as his uncle plunges his blade into his heart.

"Alex's final scream needed to be powerful, but it did shock me how intense it was," he commends. "I'm very impressed." So are we.

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