When the hoof of an undead horse marched onto the field in front of Winterfell in the Season 8 trailer, fans assumed the Night King and his army had arrived at the castle for the final showdown. Well, that may be only half true. While his army is certainly there, but the Night King might not be at the Battle of Winterfell. Remember, he was conspicuously absent from the final shot of Episode 2, as a legion of White Walkers and wights approached the Stark family home. So where is he?
It shouldn't be a surprise that the hoof in the trailer didn't belong to the Night King's mount. As viewers will well know by now, the Night King has officially taken undead Viserion as his steed — and trading a dragon in for a rotting horse would certainly be a step down. So he wasn't one of the Walkers on horseback, but is he just waiting to make a surprise entrance on Viserion's back at a crucial point in the battle? Or could he have flown the dragon elsewhere? Is the Battle of Winterfell just a distraction while the Night King is off executing his master plan? And if so, what is that plan?
There was actually a huge clue in Episode 2, "A Knight Of The Seven Kingdoms," that this popular fan theory might be correct. While Tyrion, Jaime, Brienne, Podrick, Davis, and Tormund sat around the fire on the eve of battle, the Hand of the Queen started listing the various great achievements of his accomplished drinking buddies. As he commended his brother as the famous winner of the siege of Pyke, Jaime interjected, reminding everyone in the room (and watching at home) that he was also the famous loser of the battle of Whispering Wood.
What happened at that battle again? That conflict took place all the way back at the end of Season 1, so it's forgivable if you've forgotten some of the details. At that time, Robb Stark had just marshaled the Northern forces and was marching them south to avenge the execution of his father, Ned. Tywin assumed the Young Wolf was marching to meet his own forces, and routed a small army of Northmen in an easy victory.
However, while this happened, his son Jaime was being soundly defeated in the Whispering Wood; Robb had actually split his troops, sending a small number of them to face Tywin in the field while he marched the majority of them elsewhere and surprised the Kingslayer, slaughtering his forces and taking the valuable Lannister captive.
Why remind viewers of this long-ago battle now, seven seasons later, on the brink of the Great War? Is it because the Night King is about to use a similar tactic, dividing his forces so as to take a more valuable target by surprise while the armies of men are focused on Winterfell? That certainly seems like a possible scenario.
But what would that target be? It could be the Iron Islands, since Yara just went there to prepare her homeland for Daenerys in the event that the queen needs somewhere to retreat. Everyone seems to think that islands are safe from the White Walkers; but while it's true that the wights can't swim, there's nothing to stop the Night King from flying over to Pyke on Viserion's back and burning it all to the ground.
Alternatively, there's another juicy target even farther south: King's Landing. When Jon arrived in the capital in the Season 7 finale, it was stressed just how many people live outside the walls of the Red Keep. If the Night King wants to wipe out humanity and create even more undead followers, what better target than King's Landing? He could add a million new zombified troops to his army and then march them north, converging on Jon and Dany's position from both sides.
Dany's vision in the House of the Undying involved the throne room, seemingly in ruins and covered in snow. One of Bran's many Three-Eyed Raven visions involved the shadow of a dragon flying over the red brick roofs of King's Landing. Fans have speculated for years about what those visions portended. What if the shadow of that dragon wasn't teasing Dany's arrival at the capital — but rather the arrival of the Night King, bringing winter and destruction along with him?
Not only would this strategy swell the Night King's army and trap Jon and Dany between his forces, but it would also ruin their plan for the Battle of Winterfell. As outlined in Episode 2, they plan to just hold off the undead long enough to lure the Night King out into the open using Bran as bait and then kill him, which would presumably destroy his entire army as well. But if the Night King's not there, then this plan will obviously not work. If they're unable to exploit this particular Achilles heel, they may find themselves overwhelmed and overrun by the undead, with no magic key to stopping them.