In the fifth episode of Game of Thrones' sixth season, the origins of the White Walkers were finally revealed. In an effort to stop humans from destroying the weirwood, the Children of Forest created, the White Walkers to get rid of the humans. However, the White Walkers now have a mind of their own, which was proven when they killed their own creators after Bran was branded by the Night King, leading him to the Three-Eyed Raven's cave. But why does the Night King want Bran on Game of Thrones?
The aftermath of the White Walkers attack on the cave has left Bran and Meera on their own, fleeing from the White Walkers and the Night King who seems determined to kill Bran. But what does the Night King want with Bran? Why did he want access to the cave in the first place? The Night King is smart, he doesn't just kill without reason; he attacks with purpose. Still, it's unclear what he could want with Bran. Is it because Bran can warg and time travel? Does the Night King not even care about Bran and just wanted to destroy the Three-Eyed Raven and the Children of the Forest? Is Bran just a bonus in the Night King's endless path of destruction? It's hard to tell, but one fan theory may provide an explanation.
According to Game of Thrones legend, the Wall was built by Brandon "Bran" the Builder, the founder of the House Stark and one of the first commanders of the Night's Watch. Based on present-day Bran's ability to time travel, many fans now believe that Bran is actually Bran the Builder. It's possible, knowing what he knows about the White Walkers, Bran went back in time to convince the Night Watch to erect the wall to keep the White Walkers out. Bran was also named after Bran the Builder, so it wouldn't be that surprising if Bran was actually his own namesake.
But what does this have to do with the Night King? Well the Night King knows about Bran's ability to warg, and it's unclear how long he was with the Children of the Forest before he was turned into the Night King, so he may know more about the Three-Eyed Raven and warging in general. It's doubtful the Night King would just assume that Bran had something to do with the building of the Wall, but it's possible he knows about Bran's ability to change the past and that alone would make Bran dangerous.
If the Night King has any inkling that Bran is the reason for the Wall, the Night King has very good reason to want Bran dead. If Bran dies before he goes back in time to have the Wall built, then the Wall will cease to exist giving the Night King free access to the humans, which is what he has wanted all along.
Or maybe it's not that complicated, and perhaps the Night King just likes killing people and Bran's an easy target. Who knows? In any case, Bran and Meera will need a miracle to escape the Night King on their own. Let's hope someone (cough, Benjen) helps them before it's too late.