In HBO's Game of Thrones, the Night King is a formidable opponent, a villain who poses a much larger threat to Westeros than any we've ever witnessed before. He's so fearsome with his undead army that everyone squabbling over the Iron Throne finds themselves actually working together in order to combat the literal Zombie Apocalypse in their backyard.
As with everything Game Of Thrones, there are lots of different facts and scenes that HBO has either cut or altered regarding the Night King and his kind. Fans of George R.R. Martin's books already know these tidbits that make him even more interesting.
The Night's King in the Song of Ice and Fire books becomes a legend around the time Wall is built, but the character known as the Night King in the TV series is much older than his literary counterpart. In the show, he was created during the time of the First Men, and he looks like some sort of ancient Arctic zombie who may very well have a claim to the Iron Throne, given how he looks like he's older than pretty much everyone on the entire show.
Characters are often changed from the book to the show, usually for aesthetic purposes. For example, Tyrion is much more handsome in the show than the book's Imp who is missing his nose.
On the Game of Thrones TV show, the Night King doesn't seem to have earthly ties to The Night's Watch, at least yet. In the Song of Ice and Fire series, Martin makes it clear that the creature was once the 13th Lord Commander of the Night’s Watch, which is a very interesting detail that, like so many others dropped over the years, could lead to a bigger connection.
Tracing bloodlines and positions in the Game of Thrones series often takes fans down rabbit holes into what are ultimately meaningful plots. The fact that Jon Snow is the nephew of Daenerys Targaryen, for example, had been hinted at multiple times before it was confirmed. The Night King's past position could relate to some fan theories about his plans for Jon Snow.
In a trademark dramatic twist, HBO gave the Night King a much more important origin story than the one he's got in Martin's novels. There's a fantastic scene where Bran experiences a vision of one of the First Men receiving a shard of dragonglass to the heart courtesy of the Children of the Forest, which led to the creation of a White Walker to protect them in their war.
However, in the books, there's no mention of this origin. During the Age of Heroes, there was actually already a peace treaty in existence between the Children of the Forest and the First Men, so there's nothing to tie his creation to the Children.
Wait, you didn't know that the Night King fell for a walker lady, slept with her and contracted his condition as a result? That's because that's not how it goes down on the show. While on the Night's Watch, he went beyond the wall and spotted a mysterious woman who was "white as the moon and eyes like blue stars, her skin was cold as ice."
Before you criticize the 13th Lord Commander, remember that's pretty much the same description as the vampire Bella Swan fell for. At any rate, sleeping with this woman made him the Night's King, and the two ruled together.
Nope, the Night's King didn't rule over the White Walkers as he terrifyingly does in the TV series. Instead, he led the Night's Watch, which makes much more sense in the book. He also didn't recruit humans to become members of the White Walker force, although he still did some pretty terrible things on behalf of the zombie creatures. HBO pretty much had to leave all of that out if they were going to change his whole story, and in the books the White Walkers don't even have a leader.
The youngest Bran Stark and Joramun did find out that he made some brutal human sacrifices to the Walkers with his queen, but we don't know why, or if those humans included members of his own Night's Watch.
HBO omits the apostrophe and the 's' following the Night King's name, which changes his moniker from the novel's "Night's King." This doesn't sound like a huge change, but many fans argue that it changes his entire character, especially since the reason why he was the "Night's King" was because he was also leading the Night's Watch at the same time, another omission from the show.
If show-fans knew that he was supposed to be leading the Night's Watch when he fell for a woman who was probably a White Walker, it might change some things. Also, given how many members of the Night's Watch have totally disregarded the rules over the years, it makes Jon's experience look rather severe. Then again, today's rules likely exist because of those who broke them in the past. It would also give the Night King more insight into the Night's Watch.
Some fans say that the Night's King and the Night King are two completely separate entities since there are so many differences between them. According to these fans, the Night King is a completely fabricated character designed by HBO to create yet another contender for the Iron Throne, someone to organize the threat of the White Walkers and make them a much more formidable foe than they are already.
What's more probable is that the company simply modified the Night's King into their Night King, as they've altered every single character at some point or another. Creative liberties are widely employed in the adaptation, but if you're a purist you could insist that the Night's King is omitted from the show, as many fans have argued.
In the novels, it's insinuated that the Night's King is a Stark, and many fans have speculated over the years that he's not just any Stark but Brandon the Builder himself. Given that his House and name have become a forgotten part of his legend as forbidden information among the Seven Kingdoms, we may never truly know who he is, but Martin likes to plant seeds like this to sprout into gasp-worthy moments in later books.
That's why the theory that the Night King isn't only trying to save Westeros but may actually help Jon Snow, who might be his relative, in the end, makes so much sense to fans.
Author George R.R. Martin told fans that in the books, the Night King isn't in the battle for Westeros at all, which makes the last few episodes, the loss of Viserion and the upcoming season quite different. The Night King is merely a legend who is long gone during the tale we're reading, so there's no way any of our present-day protagonists could have even met, let alone seen, the character.
Martin says, "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." Martin's books are behind the TV series at the moment, but he's alerted the team how the books will end and presumably this will all still fit in the narrative minus the Night King as we know him.
Given that he's not even around anymore in the books, it stands to reason that the Night's King, as he's known in the novels, had a legendary ending that Nan would tell tales about in modern day Westeros.
Along with his queen, the Night King terrorized Westeros to the point where the people had to unite and take them down, which is why the legends tell of Joramun (the King-Beyond-the-Wall) and Brandon the Breaker (the King of the North), along with their army of Northmen and Wildings, taking out the pair. This also freed the Night's Watch from the control of the Night's King and his queen.