Why were the WWers hanging around the edges of that rock formation forever before they closed in?
The ice was initially too thin to support their weight but solidified while they were waiting.
shareI like the theory that the Night's King has the same sort of powers as Bran, and he foresaw the chance to add a dragon to his army of the undead. So he told his wights to wait until the lake was frozen, the little island was covered in frozen pee, and Danerys was close.
And that had damn well better be the explanation, because we've seen him affect local weather conditions before. He can create killing freezes, and could have frozen the lake and mobilized the wights at any time during the waiting period.
In my opinion, there _is_ another explanation: The Night Kind just didn’t care to speed up the process of the lake freezing over. Why should he? Obviously, he’s been in no hurry at all so far. They don’t need to eat, drink, sleep or take a leak, they’re in no hurry to reach the wall… so why not simply wait?
However, I like the greensight theory much better.
It’s much more plausible than the NK saying: »How cool is that? We stand here waiting because we don’t have anything else to do, but then they deliver us the ultimate weapon! What luck we didn’t attack earlier!«
Moreover, it explains why the WW brought along all those chains: Because the NK knew that they’re going to need them. He might even have known it last time they were active (I think they said it was a thousand year ago or something?) so they collected the chains somewhere back then, which again explains why the had a bunch of very massive chains at all.
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