The young warg, Bran Stark who was recently marked by the Night King surely means something big. In the spreading reports, there is a theory that Bran will bring destruction to everything in "Game of Thrones." Bran who is said to head north might accidentally allow the white walkers to cross The Wall.
Remembering the fifth episode of Season 6, it was shown how Hodor got his condition way back in his childhood. His condition was caused by Bran's powers. That moment when Hodor sacrificed himself to block the door so Bran and Meera could use some time to escape seemed to connect to his mind during his childhood.
In that episode, it seems that Bran's power is bringing a bad fate to everyone. The mark left by the Night King on Bran's arm while time travelling is like an indication that doom is coming to the seven kingdoms. Season 6 so far is the best of all "Game of Thrones" seasons because it resolved a lot of past theories and answered a lot of hanging questions in the previous seasons.
According to Independent, it was known that Bran accidentally allowed the white walkers to infiltrate the magical protection of the weirwood cave where the three-eyed raven was hiding. It was noted that The Wall uses the same magical protection of the weirwood cave when the ancient character known as "Bran the Builder" built the wall.
Now that the young stark's only possible route is going north through The Wall, this could be the reason why the Night King did not chase and kill Bran. He wants Bran to go through The Wall so that he and his white walker army can infiltrate The Wall's magical protection. If the theory is right, the Night King will surely start a bloody battle in Castle Black.
The interesting part of this theory is it shows an irony of the ancient character known as Bran the Builder of the Wall and the current young Bran Stark who will be the destroyer of The Wall. There is also one big speculation about the ancient character named Bran the Builder. As posted by Refinery29, it was known that Bran could travel through time so this could possibly mean that he was the ancient man described in the past eight millennia called as the Bran the Builder with great powers.
Below is a video about the origins of Bran the Builder