Someone call HR, conditions on The Northman set sound positively medieval. “I was so exhausted that I wanted to cry,” said star Alexander Skarsgård last month, remembering his time on Robert Eggers’ brutal Viking epic. “The days were really long and hard, and I got shackled and dragged through the mud.”

The cast might not have had a good time making The Northman, but you will watching it. Based on a Norse legend, the film follows Amleth (Skarsgård), who as a child witnesses the bloody murder of his dad, King Aurvandil (played by Ethan Hawke). Fast-forward several years and the culprit, Aurvandil’s scheming brother, has married Amleth’s mum (Nicole Kidman, continuing her round-the-world tour of accents) and made a mess of his empire. The next two hours see a grown-up, hulk-like Amleth – nothing like childhood trauma to fuel late-night gym sessions – pose as a slave in order to infiltrate his uncle’s inner circle, hoping to get revenge.

It’s all properly violent and uncivilised. Director Eggers is known for mixing wacky surrealism with explicit violence (see The Witch, The Lighthouse), so don’t expect wall-to-wall blockbuster action though. We get Willem Dafoe playing a Gollum-like court jester with Willie Nelson’s pigtails, and Finchy from The Office (Ralph Ineson) pops up in what looks like Adam Ant’s earrings. Perhaps the most bonkers bit is when a no-eyed Björk whispers her prophecy to Amleth, in full, feathered seeress costume. If the Icelandic icon’s next album is all Viking drinking songs, we won’t complain.

And yet for all the weirdness, Eggers’ gruesome ode to Hamlet packs its biggest punch during the fight scenes. You’ll wince into your popcorn when Amleth slices a henchman’s nose off, baring the raw bones beneath. And the climactic battle on top of a fiery volcano feels like Gladiator doing Star Wars: Revenge Of The Sith. Don’t expect the loser to return as an asthmatic cyborg though, Eggers isn’t the sequel type.

Elsewhere, the star-laden cast break out of their comfort zones. Kidman doesn’t often venture into the arthouse, but she’s clearly having fun here. Her Queen Gudrún seems a classic Shakespearean victim, though subtle looks and knowing glares tease an altogether different character ready to spring into action. Then there’s Olga, a slave with supernatural powers who forms a romantic bond with Amleth. Both provide a pleasing update to the genre’s usual formula of wives and mothers watching on from the sidelines.

If there’s one criticism to be made, it’s that the more avant-garde moments sometimes turn tedious. Dafoe is best when he’s freaking out, but an early rite-of-passage sequence that ends in an orgy of burping and farting seems silly – even if it does soften up the viewer for a shocking plot twist. Later, a mounted Valkyrie with braces flying through the sky tries to add layered meaning, yet causes confusion instead. Tone down the oddness, however, and you’d just have another gory historical snoozefest. Eggers’ style is totally unique and he’s obviously enjoying himself, even if his actors might not be.