The topic of the Night’s King had been a talking point for many fans who have read the books and watched the show, especially after the end of last season, wondering if the show is taking a different route with the character or if they’re revealing Winds of Winter material. GRRM responded to one’s fan question in the comment section of his blog today that seems to make the answer clear. (Spoilerishness abound!)
ADragonDemands, who states he is an editor for the Game of Thrones Wiki, asked:
Starting with the episode “Hardhome”, the TV writers have started openly referring to the White Walker leader as “the Night King”. Back in Season 4 the online guide also briefly listed him as “The Night’s King” but was hastily taken down, apparently a leak. The online guide now calls him “The Night King”.
Everyone in the media is now assuming that this “Night King” is the SAME character as the legendary “Night’s King” fought by Joramun 8,000 years ago. I’m concerned if it’s just a TITLE, like “Storm King”, so there can be more than one - given that it was said the Night’s King was killed.
Now I want to ask “are these indeed the same character?” but I know you probably won’t reveal upcoming book material. Better phrasing might be “is it appropriate to treat these as one character on a single article on the wiki, or should we split it into two articles? Or at least two sections on the same article?”
And then Martin replied:
As for the Night’s King (the form I prefer), in the books he is a legendary figure, akin to Lann the Clever and Brandon the Builder, and no more likely to have survived to the present day than they have.
So no, the “Night King” isn’t a title passed down for the ruler of the White Walkers, nor is the legendary “Night’s King” still fighting today. It makes sense the show would want to give the character a name/title though.
He also addressed a slip by Mance referring to King Maegar the III (who isn’t in the books) by saying either he was invented for the show or that it was an intentional mistake on Mance’s part to show he is not that competent with Westerosi History.