[Smithy]

Originally Posted by The Slim Reaper

Spoiler:

The thing that's baffled me the most after the 2nd episode, is that the NK wasn't supposed to be the archetypal good vs evil villain, but then Bran said "yeah, he just wants to kill everyone, lol". There has to be more to it than that, so maybe when he turns up to kill Bran we'll get some more info in a vision or something.

R.I.P Theon.

My theory

Spoiler:

in the original Great War against the walkers there’s no way the first men would have stopped them, so some agreement must have been made, presumably involving sacrifice to them (via Craster or whatever) over time that deal has been forgotten and broken and now they’re marching to kill everyone because the deal was broken. The NK only started collecting an army and marching AFTER Sam and Gilly escaped with the baby, before that the only time the white walkers killed was probably when wildling encroached on their territory