The big question after last episode is 'Did the Night King know it was going to happen?', that the Night King knew exactly what was going to happen, and had set it all up. The convenient single Wight left after Jon kills the White Walker, the 3 dragon-killing spears the WWs had with them, the dragon chains.

I'm watching through the whole series again right now, and I just realised that in S2E10 a White Walker looks directly at Sam, knows he's there for sure, then just ignores him and marches on. That never made any sense to me, until now. What if the Night King has been planning everything from the very beginning? He left Sam alive because he needed him to be alive to get to where he wants to be. To keep Jon alive, to get him to the North, to call Daenerys for help, to get the dragon, and probably much further.

To me, that's more terrifying that any undead dragons, giants or enormous army. How do you defeat an enemy that knows exactly what's going to happen? The Night King is playing chess, the living are playing Connect 4.