Did The Tourney At Harrenhal Start The Night King's March?
One of the major public events and contributing causes of Robert's Rebellion was the infamous Tournament at Harrenhall everything that happened at what was the biggest tournament of its time had far-reaching implications. Nearly every prominent family in Westeros was represented in the audience as Crown Prince Rhaegar Targaryen shamelessly flirted with Lyanna Stark in front of everyone. When he crowned her Queen of Love and Beauty after winning the joust, he basically made their affair official in front of his wife Elia and Lyanna's fiancé Robert Baratheon. Slightly less noteworthy, but perhaps just as groundbreaking was the fact that the entire Stark family was in attendance leaving Winterfell empty for a period of at least several weeks. Meera Reed recounts in great detail the Tourney for Bran's benefit, and she clearly mentions all four Stark children, Brandon, Lyanna, Eddard and Benjen. She doesn't specifically mention Rickard Stark, but that doesn't mean the Stark parents weren't in attendance, and it's more than possible they would've attended.
While we only see the first White Walker 15 years later at the top of Game of Thrones, we know from Wildling movements that they’ve been actively moving south for some time. In the books, Martin goes out of his way to point out that it’s around the time of Robert's Rebellion, that Mance Rayder starts uniting the Wildlings in preparation to invade the south, all to escape the Night King.
Granted, the awakening of the White Walkers is kind of a big event to hang on a technicality, so it may have more to do with the Starks being so far away from the North rather than their Winterfell itself. Though the idea of White Walkers rising in the North as unwitting humans party and make trouble in the South rings with some nice symmetry... Either way, the idea of a Stark as a watchperson against the night is in line with themes in the show, and it would stand to reason that if a Stark left his spiritual post, something bad would happen. That is literally what happens to Ned’s father, sister and brother, and the following generation of Starks fairs no better in their own diaspora.
Also, it’s important to remember that the White Walkers waking up is just a small piece of why the second Long Night is coming and with such force. It may have been a Stark absence that allowed them to rise, but once the White Walkers started gaining power, there should have been huge contingency plans in place. Unfortunately, too much time had elapsed between confrontations for early defenses to have been maintained and for the populous to remember to fear the Others. This second confrontation seemed destined to happen as the Westerosi population enjoyed years of relative (relative) peace in the wake of the White Walkers’ first invasion, which makes sense given their position as a metaphor for death itself. To quote Berric Dondarrion, “Death is the enemy. The first enemy and the last. The enemy always wins, and we still need to fight him."
What Does This Mean For Game of Thrones Season 8?
If it was indeed a Stark not being present in Winterfell that somehow contributed to the rise of the Night King, what happens when they’re back? Clearly once Sansa and Jon regained control of the castle, no magic sleep spell overtook the Night King and sent him and his armies back from whence they came. Whatever magic was at work in keeping the White Walker at bay isn’t going to be of any help now that Viserion is an ice dragon - that much was clear from the Game of Thrones season 7 finale. However, that doesn’t mean Starks getting back home won’t make a practical different in the war to come.
Putting aside any magical benefits to a Stark being in Winterfell, the fact that the Stark family is in power and the North is united behind them once more can only mean good things for the human side of the Night King/Human conflict. Sansa and Jon together are not only actively preparing for a long winter, but also for a prolonged war during said winter. The Boltons wouldn’t have prepared for this war, nor would the Umbers or the Karstarks. Sansa’s an able leader who thinks of small details like ensuring armor gets lined with leather so their soldiers don’t freeze. Also, big details like snagging the Knights of the Vale into her service and keeping them there to shore up defenses could make a huge difference in the actual fighting that will occur. There's also Jon, literally a mythical hero come back to life. As the “son” of Ned Stark, he gives the people something to rally around.
The Starks are just as important as beacons of hope, safety and inspiration as they are magical wards against the unknown, and while nobody's expecting a purely happy ending to Game of Thrones, what glad tidings fans will get probably take the form of season 8 concluding with Winterfell remaining in Stark control. It’s the way it should be, both spiritually and pragmatically.