12 Biggest Unanswered Game Of Thrones Mysteries
5. Who Is The Night King (And What Do The Others Want)?

The Night King, while not a figure in the books, is the biggest threat to all of Westeros and the one who must be defeated above all others.
We seemingly saw the creation of him when the Children of the Forest made the first White Walker, since the human was played by the same actor as the Night King. There's a good chance he's a Stark (no, NOT BRAN), and perhaps who he really is doesn't ultimately matter, but given he's the overarching villain it'd be interesting to know who he was - especially since if they are the same person it means he's been around thousands of years, and survived the first time the White Walkers were beaten back.
Indeed there are many mysteries wrapped up in this: what, exactly, are the White Walkers/Others, and what do they really want? In the show at least they largely seem to stand for death, but could there be more motivation to them in the books?