Go Behind The Scenes Of That 'Game Of Thrones' Giant Frozen Lake Battle

Last night's Game of Thrones episode, entitled "Beyond the Wall," featured yet another ambitious battle scene as Jon Snow, Tormund Giantsbane, Ser Jorah Mormont, and a few other fan-favorite characters went on a mission in the icy wastelands north of Eastwatch-by-the-sea and faced off against the Night King's army of the dead.

And much like they did after this season's "The Spoils of War," HBO has now released an in-depth behind the scenes video that details the tricky techniques the production used to achieve many of the episode's biggest and most explosive moments. This should go without saying, but there are obviously huge spoilers for last night's episode in this video, so consider yourselves warned if you haven't caught up. Check out the detailed video below.

Showrunners David Benioff and D.B. Weiss are spot-on when they talk about how using the real location enhances the episode's reality in a major way, because it's clear that they went out to some real-life icy locations to film those scenes of these characters trudging toward the fight. And while aspects like the wights and the dragons are obviously created using visual effects, this video clued me to one effect I didn't notice: the production built the whole "frozen lake" set themselves, and were able to seamlessly transition from an actual windswept, icy location to a controlled set.

Benioff and Weiss tend to come off as pretty laid-back, restrained guys in these featurettes, but you could sense them perk up a little when talking about the zombie polar bear, something they've clearly been excited about incorporating for a while. And while the video is stuffed with cool tidbits about things like dragonfire explosions, the challenges actress Emilia Clarke faces as she acts opposite nothing when she's supposed to be on Drogon's back, and Kit Harington's disdain for being shoved into a water tank while wearing his full costume, I think my favorite part of the whole thing is hearing Rory McCann – who plays the scarred Sandor "The Hound" Clegane – completely fail to use his imagination when he's working with that bear.

"I've never really worked with this ping pong ball thing, and 'pretend that's a bear,'" he says. "I've had people going, 'when I come towards you, I'm a bear.' No you're not. Your name's Toby!" Rory McCann is the best.

The season seven finale of Game of Thrones airs this coming Sunday night on HBO.