My original tinfoil was that when Tyrion said if he had been outside during the Battle for Winterfell, he might see something someone else was missing, it was a hint that there would be a subtlety that was a large clue. I was obsessed with the little head cock the Night King gave Bran during their staredown. Then, when Dany glanced at the Red Keep from on Drogon, I mistook the birds flying around for crows. I convinced myself the big twist was that the three eyed raven was a greater danger than anyone had assumed, and that perhaps the Night King wanted to exterminate it for understandable reasons. I knew GRRMs original outline had Bran moving from wanting to learn magic to save his family to wanting to learn magic for magic 's sake, so this seemed in step.