Alexander Skarsgård recalls filming a fight scene in The Northman with The Mountain from Game of Thrones. Robert Eggers’ latest draws on Scandinavian folklore for an epic revenge tale set during the age of the Vikings. Skarsgård plays Prince Amleth, a young man bent on vengeance after the murder of his father.

The germ of this classic revenge tale should of course sound familiar, as it long-ago formed the basis for Shakespeare’s Hamlet. Eggers’ take on the story of Prince Amleth did not however require its star Skarsgård to learn loads of Shakespearian dialog. The challenge of being in The Northman was instead more of a physical one for Skarsgård, who has previously spoken about the exhausting experience of helping Eggers bring his epic Viking story to life.

Related: Where The Northman Was Filmed (& How Much Was Really Iceland)

It turns out one particular scene in The Northman proved especially physically demanding for Skarsgård. Speaking to EW, the Prince Amleth actor recalled squaring off against the imposing actor Hafþór Júlíus Björnsson, who of course is best-known for playing Gregor Clegane aka The Mountain in Game of Thrones. Skarsgård admitted to being intimidated by the 6-foot-9 Björnsson even before they shot together. Then when they did their scene, he found out exactly what happens when you are called upon to battle one of the world’s most powerful physical specimens:

"He tried to go easy on me, but he still has to tap me lightly and I just went flying. I was definitely quite sore after that week of filming. You do not want to fight the strongest man on the planet."

Skarsgård’s own impressive physique has of course been heavily featured in marketing leading up to the release of The Northman. But as strong as the ripped Prince Amleth actor may look, he clearly is nowhere near as powerful as Björnsson, a man who once made his living winning strong-man contests, at one point holding the official title of World’s Strongest Man. Björnsson’s massive size and imposing presence was of course previously put to memorable use on Game of Thrones, in which he played Cersei Lannister’s hulking undead protector Gregor “The Mountain” Clegane. A fan-favorite character on GoT, The Mountain ultimately received the send-off viewers were hoping for when he did epic battle against his own brother Sandor “The Hound” Clegane in the series’ final season.

After Björnsson’s memorable turn as The Mountain on Game of Thrones, it makes all the sense in the world that Eggers would incorporate the actor into his own fantasy-adjacent film The Northman. And going by Skarsgård’s account of their on-set square-off, it seems Eggers got exactly what he wanted from the real-life Icelandic man-mountain. Skarsgård may have indeed taken a beating in more ways than one during filming of The Northman, but it seems to have been all worth it, given the largely positive critical and audience response to Eggers’ Viking epic.

More: The Northman Cast & Character Guide

Source: EW

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