Actor Vladimír Furdík took over the role of the Night King from Richard Brake in season 6 of Game of Thrones - but what was the story behind the recast? The Night King first appeared during Bran's vision in the season 4 episode "The Lion and the Rose," and Brake played the leader of the White Walkers in a total of three episodes over the course of season 4 and 5 before he was replaced.
The Night King was a key antagonist in the later seasons of Game of Thrones. In season 6, one of Bran's visions showed a captured member of the First Men (played by Furdík) being turned into the very first White Walker by the Children of the Forest, who stabbed him with a shard of Dragonglass in order to transform him. He then gained the power to convert others into his fellow White Walkers (like the poor sons of Craster), who in turn had the ability to reanimate the dead. With the White Walkers on his side and his Army of the Dead, he was nearly unstoppable - until he met Arya Stark. But why was the role of the Night King recast in the middle of his arc?
Brake portrayed the Night King for only a few episodes, but they were important in explaining his immense power. He was in the role when the Night King turned Craster's final baby son into a White Walker with the touch of a finger. Brake was also still around for the episode "Hardhome," which was the first time that Jon Snow killed a White Walker using a Valyrian steel sword. The Night King never spoke a word but his icy blue glare was enough to understand that the living had a new enemy. By the time the Night King reappeared in season 6, the role was played by Furdík - but to this day there's no real explanation behind the recasting. In an interview with EW, Furdík revealed that even he doesn't know why he took over the role.
"I don’t really know why they cast me. When we did season 5, I was the White Walker who fought Jon Snow [in “Hardhome”] — the first time Jon Snow killed a White Walker, that was me. After that, [showrunners David Benioff and D.B. Weiss] asked if I’d play the Night King for seasons 6 through 8. I never asked why. Maybe they were happy with what I did in season 5."
As explained in the interview, before Furdík became the Night King, he played the very first White Walker that Jon killed. He also served as a stunt performer and stunt supervisor on various episodes from season 5 and beyond. Even though the Night King role was more extensive, Furdík had no qualms about his new part in the HBO series.
It's very possible that Game of Thrones wanted to go in a new direction with the Night King based on Furdík's stunt work. The Night King was much more active in season 6 and beyond and it seems likely that Furdík made an impression in battle as the season 5 White Walker. During Furdík's portrayal, the Night King led the assault on the Three-Eyed Raven's cave, attacked Jon's men during the Wight Hunt, and traded in his horse to instead ride an ice dragon. He may have been mute, but he was a menace nonetheless.
Since the Night King had been alive for thousands of years during Game of Thrones, it's plausible that he might reappear in the prequel series heading to HBO in the near future. That series will focus on the first Long Night, when the White Walkers brought terror and darkness to the land, and the official synopsis teases that it will reveal "the true origin of the White Walkers."