Wielding a flaming sword on a glacier for weeks on end is not fun, but it does pay off.

There are spoilers from "Game of Thrones" Season 7, Episode 6, "Beyond the Wall," below.

Returning to "Game of Thrones" midway through the current season, Richard Dormer had to quickly get back into the swing of things. His character, Beric Dondarrion, joined Jon Snow (Kit Harington) on the mission beyond the wall, which meant that Dormer spent five weeks shooting the icy battle that ensued. The actor recently described the experience as "hellish" while speaking with Variety but conceded that "it was worth it."

"It was like running a marathon in about 40 kilos of armor and seal skin, with only one eye and a flaming sword that kind of blinded my one good eye," Dormer told the publication.

His sword was actually flaming, and that made everything harder. The flames only last about two minutes at a time, according to the actor, so they had to stop and get it going again frequently. Plus, moving it too quickly made the flames go out, so he had to be mindful of his swinging speed.

"You've got to move just slightly slower but more effort, you know?" he said. "Also it weighs three times as much as a normal sword, so it's just this big club really."

More members of the show's cast and crew expanded on how complex it was to shoot the battle in a behind-the-scenes video released Monday, and Dormer wasn't the only one who thought it was rough. Harington described being plunged into cold water in his full costume as "miserable," and showrunner D.B. Weiss recounted actors slipping and falling on the Icelandic glacier where they filmed.

Like Dormer said, though, it was worth it.

The "Game of Thrones" Season 7 finale airs Sunday on HBO at 9 p.m. ET/PT.

[via: Variety; HBO]