Bran Stark has managed to survive seven seasons of Game of Thrones against all odds; his attempted murder was the big surprise at the end of the series' pilot episode. But the more Bran develops his psychic powers, the more Game of Thrones suggests that Bran might become a villain by the end of the series, rather than a hero worthy of the Stark name. Game of Thrones has even been dropping hints that Bran could become the Night King, the ultimate bad guy and the biggest threat currently facing Westeros. While on its face, the theory seems absurd — several characters have already seen the Night King in the present timeline, where the young Bran Stark already exists — Game of Thrones does love to surprise its viewers, and this would surely be a shocking revelation.
The series' viewers are often one step ahead of the writers, especially those that know George R.R. Martin's A Song of Ice & Fire book series inside and out. And slowly, the Bran will become the Night King theory has been gaining steam. For example, Reddit user turm0il26 theorizes, "Bran believes he is eventually (with more knowledge) going to be able to rewrite history and that's why he decides to go back and stop the Night [K]ing several times, but fails every time, ending up fulfilling the timeline-circle and taking the identity of the Night [K]ing himself."
And if you look back at what the show has presented so far, there are actually plenty of clues and hints sprinkled throughout that could be suggesting that Bran will become Westeros' worst nightmare.
He's Demonstrated His Warging Abilities
Bran can't walk on his own, but as he works on his abilities, Bran can travel into the minds of other creatures. He was able to control Hodor and a crow. Maybe this ability is a hint that Bran will control the Night King, rather than age into him or transform into him.
He Has "Changed" The Past
Bran has already created one time-travel related paradox: Remember "Hold the door?" By warging into Hodor's body in the past, Bran created the brain injury that left Hodor only capable of saying a single phrase for the rest of his life. As the Three-Eyed Raven told Bran, "the ink is dry," meaning, if Bran continues to mess with time, the consequences will already affect the present.
The Hound's Vision
In the Season 7 premiere, Meera and Bran finally reach the Wall, just after Jon left to become the King of the North. Later, the Hound's firey vision of the Night King slowly approaching the Wall and, ultimately, destroying it, could mean that Bran's presence at the Wall is connected to the Night King.
He Saw The Night King's Creation
While he was training with the Three-Eyed Raven, Bran saw the moment when the Children of the Forest created the Night King, the very first White Walker, in order to fight a war against men. Bran's reaction to watching this scene was to wince, as though he was the man being transformed. It may have seemed like just a filmmaking tactic to make the scene dramatic, but perhaps Bran's pain was a hint that he will go back in time to save the children of the forest.
Children Of The Forest's Confession
Another small hint in the same creation scene — when Leaf explains why the children resorted to creating the Night King, she says "we needed to defend ourselves... from you." After a significant pause, she adds, "from men," to make the statement more general. But perhaps Bran will travel back in time in order to save the children from his own timestream meddling by allowing them to transform him into a monster.
Men Can Become White Walkers
The White Walkers have increased their ranks by converting Craster's infant sons into their undead progeny. Bran is a magically gifted individual, so it's possible that this ability could be explained not only by the Night King's origins, but by Bran's powers acting as a conduit.
Bran Was Touched By The King
While attempting to spy on the Night King, Bran was not invisible, as he was in most of his other visions, and when the King grabbed him, leaving a hand-shaped scar on his forearm, the White Walkers were able to penetrate the magical barrier in the Children of the Forest's stronghold. Maybe the reason the Night King was able to see Bran was because the two are already psychically connected because they're the same person.
Bran Already Has Other Identities
Jojen called Bran the "raven," referring to Bran's training with the Three-Eyed Raven, and, perhaps using his greenseeing powers to know that Bran would eventually become the Three-Eyed Raven. And after the Night King grabs Bran, the Raven says, "it's time for you to become me," another suggestion that Bran may adopt different identities throughout his life in order to ensure the fate of the world.
It may not be canon yet, but if Game of Thrones wants to make Bran Stark the Night King, the show has effectively laid down enough hints to make it totally plausible.