Quote Originally Posted by Tbonewannabe View Post
I am thinking it is the horn and she maybe goes to the Wall because Jon talks Dany into going to the wall to see the White Walkers. Cersi being the cunning yet dumb bitch that she is blows the horn and brings down the wall. People then unite to fight them because enemy of my enemy.

Completely random theory coming out of my head. I haven't seen anything that would suggest any of that is true.
I think the horn in this case is one that controls dragons not the one that supposed to bring the wall down.