Here’s How Game of Thrones Turns People Into White Walkers

Game of Thrones is offering fans a behind-the-scenes look at exactly what goes into bringing White Walkers to life. The HBO drama’s latest featurette focuses on prosthetic designer Barrie Gower explaining the detailed and lengthy process of creating the unearthly look of Westeros’s biggest threat.

Read More: Watch the New Game of Thrones Season 6 Trailer

Gower walks viewers through his team’s operation, from designing the prosthetics to actually applying the makeup to actors. He also speaks about his favorite memory of working on the show to date — filming “Hardhome,” the eighth episode of season five. “It was very cold, wet, muddy, smoke, snow — we had it all going on,” he says. “We were covering [the actors] in loads of rubber each day. At times it felt like pandemonium and then you’d just look across and have a look at the monitor, and it was so cleverly choreographed and orchestrated. You couldn’t believe that what you were seeing on film was what was right next to you.”

The sixth season of Game of Thrones will premiere on April 24 on HBO.