I saw 1 episode the one where Sean Bean was killed
The first thing that popped into my head was that HBO would try to connect him to Donald Trump.
My completely speculative opinion is that things go so badly for The Living in the coming war that Bran has to time-travel back, become the Night King, and hobble The Deads’ effectiveness. < /guess >
Pure speculation, but I suspect he is a relative of Bran. Bran is the oldest living male Stark now, rightful heir to Winterfell. The night king was/is house stark, probably related to Bran the builder, the first men, and potentially the first leader of the Knights Watch. Bran, as the three eyed raven, can see through time. So can the Knight king(knight not night), so they may be relatives or the same person.
Times have changed though, and modern surveillance techniques result in him getting busted while stalking his prey.
Game of Thrones is a retelling of the Norse myth of Ragnarok.
Bran is the wolf (Stark’s sigil) Fenir, son of shapeshifter Loki (Three eyed Raven), who is bound (crippled) by Tyr (Jamie Lannister) who loses his right hand. Fenir’s wild and unpredictable brother (in the weirwood network) Gamr (Night King) and Tyr (Jamie) end up killing each other.
Lannisters are the good guys, and Starks are the bad guys.
Night King is a powerful magic weapon of the Children of the Forest against their enemies, the First Men. He was created using the King’s blood of a Stark, the King’s of Winter.
He is finally destroyed through the King’s blood sacrifice of the Prince who was promised - the baby of Rhaegar’s lineage, that Danerys now carries from Jon Snow.
“theories about the Night King”
He is a Stark, and there is an empty tomb waiting for him in the crypts of Winterfell.
Samwell Tarley breaks out the magic Horn of Winter that he has been lugging around since he found it at the Fist of the First Men. Blowing it resurrects all the Kings of Winter from the Crypts - possibly even including the dead Night King. After the crisis is past, they all return to their graves, including the Night King. Jon or Bran then replaces him. Blowing the horn to start the climatic battle would make Sam the equivalent of Heimdallr (who kills Loki) in the Ragnarok theory.
Alternatively, Samwell Tarley finds a cure for the cursed Night King in the books he brought from the Citadel (green Dragonglass), that restores his human form, and allows him to find rest in his rightful tomb in the crypts.
Interesting article: https://www.forbes.com/sites/paultassi/2019/04/21/the-game-of-thrones-night-king-spiral-mystery-has-officially-been-solved/amp/
I’ve come across some interesting theories about the Night King. Anybody have any guesses on the history of this villain?
In Season 7 when Bran was being made into the Three-Eyed Raven, in one of the middle episodes told how the Night King came to be was told. As Bran was in the cave and the then Three-Eyed Raven was showing Bran visions of the past, there was a female creature in the cave/tree with him (I forget their names at this moment). In the episode, the creature is shown driving a dagger of obsidian into a male’s chest. When the dagger is all the way in, the human male’s eyes turn blue. Bran then exclaims they made the Night King. Her response was they did it because they were at war and were being killed - by humans. That was how the Night King was created.
Either a brother of the Stark Lord so has Stark blood or a bastard of Winterfell who was a Snow himself.
“theories about the Night King.”
He is coming to claim his Night Queen - Danerys or Cersei.
He is heading to the Isle of the faces, to stamp out the last of the Children of the Forest, and their wierwood network - that is where the battle in episode 5 will be.
He is coming to stop Bran from going into the past and becoming him.
He just wants to conquer everybody, like most of the other Kings/Queens.
He (Ice) is coming to return balance to the world after the rebirth of dragons (fire).