If you’ve felt a recent urge to unleash your inner Viking, you’re not alone: millions of people have been riding the waves, swigging mead and slaying the enemy in a craze for the video game “Valheim”.

Designed by a tiny Swedish games studio, “Valheim” has proved an unexpected smash-hit, selling five million copies since its early-access released last month on the online gaming platform Steam. At one point, more than half a million people were playing online simultaneously.

We didn’t expect this kind of success at all,” said Henrik Tornqvist, co-founder of Iron Gate, the company behind it. We are overwhelmed, humbled, and under a lot of pressure.

The five-strong team that developed the survival game have not yet been able to meet up to celebrate due to the pandemic, Tornqvist said.

“Valheim” players can learn to hunt, make armour, build Viking longhouses and eventually slay terrifying monsters as they explore the vast and fantastical world.

It’s quite a refreshing game and a really great one, whether you’re talking about the light, the backdrop or the music,” said 25-year-old player Pierre Galissant, who has already spent 60 hours roaming its plains, forests and swamps with three comrades.

Tornqvist suspects the ability to team up with friends is part of the game’s appeal.

“Our game being co-op focused is part of our success for sure,” he said. “And also the Viking theme.”

“Valheim”, which is still in development, is just the latest hit video game set in the vital and violent world of medieval Scandinavian warriors.

Norse mythology has inspired game designers for decades, from the late-90s series Baldur’s Gate to strategy games like Age of Empires II.

But Jean-Christophe Piot, a writer and host of a podcast about mythology, said there had been “a real revival” around the seafaring Vikings, who raided, traded, and settled around Europe between the 9th and 11th centuries.

Norse influences are hardly new in pop culture, he pointed out — Marvel Comics introduced Thor, god of Thunder, as a character in 1962.

“But they’ve appeared in video games on an unprecedented scale in recent years,” he said.

Iron Gate consciously chose this setting for “Valheim” because of the existing Norse craze, Tornqvist said, citing the 2013 TV series “Vikings” as a contributing factor.