(Spoilers for season 7 of Game of Thrones will follow. You've been warned.)
Bran Stark is probably the most curious character on Game of Thrones. He escaped death from the very beginning—literally in the very first episode of season 1. And he's been avoiding it ever since. At first, through sheer luck, then via a squad of protectors, and now, being back home in Winterfell. But now that he's the very weird, mostly inactive new Three-Eyed Raven, Bran is starting to look a little funny in the light. Suspicions about his role in the great fight against the undead have been rising for at least weeks, if not months, but one theory is hitting a fever pitch now that there’s only one episode left in season 7.
Despite having no use of his legs, Bran is incredibly powerful. In addition to being able to warg into, or possess, humans, Bran also has greensight, visions, and dreams of prophecy. He can revisit the past and see the future, as evidenced by the tragic moment the young Wylis becomes Bran’s former protector, Hodor, and in the scene where Bran calls out to his father Ned when the elder Stark is a young man, attempting to rescue his sister, Lyanna.
Reddit user turm0il26 is one of the latest to lay out the argument that Bran will become the Night King. That's right: the last male heir to the Stark family throne could be the fucking worst sentient being in the Seven Kingdoms and beyond. The theory starts with the fact that Bran has been continuously going back in time to try and stop the White Walkers from destroying mankind. But as both Bran's old guide Jojen and the OG Three-Eyed Raven warned Bran: you can’t remain in the past or in someone else’s body for too long. “It is beautiful beneath the sea; stay too long and you drown,” the Raven said.
One of the most important moments of Bran’s journey from regular kid (or, as regular as a kid can be in Westeros) to the new Three-Eyed Raven is when he witnesses the Children of the Forest create the first White Walker. The Child who explains why they did it tells Bran it was done to protect them from humans. In the scene, the first man-turned-White Walker gripped the tree he was bound to in the exact same way Bran gripped the roots beneath the ground as he watched, leading some to believe Bran was experiencing it in the moment because he was that man. That’s how Bran could have gotten trapped in the first White Walker, becoming the Night King who possesses all of Bran’s powers.
Another part of this theory centers around the moment where Bran tries to warn the Mad King, Daenerys Targaryen's father, about the final battle to come. Both the books and the series point to the fact that the Mad King became mad after Bran attempted to warn him about the White Walkers. His final order was, "Burn them all," which could have been Bran's advice about how to deal with the White Walkers.
Last but not least, fans have pointed to the moment in season 5 where the Night King spots Jon Snow at Hardhome, and lets him escape. The leader of the White Walkers is known for being horrendously ruthless and unforgiving, so why else would he have let Jon go, if not because he was related to him? Additionally, George R.R. Martin has let on that the ending of the series will be bittersweet, possibly meaning that Jon will kill the Night King Bran to end the war once and for all. That would be the definition of bittersweet.
Another theory about Bran's identity suggests he may be one of the legendary Brandons he hears about in old folk tales; in particular, "Brandon the Builder," who built both the Wall and Winterfell to shield off the White Walkers. But that's nowhere near as fun. Fingers crossed we find out more about this theory in the final episode of the season.