Warning: HUGE Game of Thrones spoilers below, so proceed with caution.
There's a particular scene during the bloody Battle of Winterfell in Game of Thrones that makes it clear just how far Arya (Maisie Williams) has come since the first season, if you somehow hadn't already noticed. She's up on the wall of her family's ancestral home, effortlessly taking out wight after wight with her fancy new dragonglass spear in a way that actually, genuinely made me say out loud, "Wow." (To be fair, it's not the first time she's made me do that.)
From scrappy pre-teen, to bloodthirsty Faceless Man, to a full-blown Stark warrior, Arya has had quite the journey over the course of the last eight seasons, which culminates in the battle against the White Walker army in season eight's third installment, "The Long Night." Not only does she knock out a ton of wights during her perilous journey through the halls of Winterfell, but Arya also manages to take out the icy big bad himself — yes, Arya Stark kills the Night King.
If you'd asked me who would eventually kill the villain just last week, I likely would've volunteered Daenerys Targaryen or Jon Snow for the role, and not until the season's penultimate episode or even the series finale for that matter. They're the ones who all those prophecies are supposed to be about, right? But showrunners D.B. Weiss and David Benioff pulled a fast one by having the honor of killing the Night King go to Arya, who stabs him with her Valyrian steel dagger in the Godswood while protecting Bran.
"It was so unbelievably exciting," actress Maisie Williams told EW of the scene, before noting that she initially worried fans wouldn't accept the shocking scene. "But I immediately thought that everybody would hate it; that Arya doesn't deserve it. The hardest thing is in any series is when you build up a villain that's so impossible to defeat and then you defeat them. It has to be intelligently done because otherwise people are like, 'Well, [the villain] couldn't have been that bad when some 100-pound girl comes in and stabs him.' You gotta make it cool. And then I told my boyfriend and he was like, 'Mmm, should be Jon though really, shouldn't it?'"
Although the more obvious heroes in the HBO fantasy series — Jon, Dany, even Jaime or Brienne — seem like they'd be far more likely candidates for such an important plot twist, it actually makes total sense that Arya would kill the Night King for a variety of reasons.
Most simply, she's been training for this ever since she witnessed her father's head get chopped off in King's Landing. Arya has dedicated the better part of her life to becoming capable and strong enough to finally defend not only herself, but her family. Sure, Cersei is still on her list, but this is one more step toward righting the wrongs against her family. She's small and therefore easily underestimated, both of which she uses to her advantage in this moment.
To further understand how full circle this kill is for Arya, we also have to take into account where it happens. Think back to season seven's fourth episode: after Littlefinger gifts Bran the Valyrian steel dagger — which basically started the War of the Five Kings after an assassin tried to kill little Bran with it in season one — he immediately passes it onto Arya during their conversation in the Godswood. Now, why would the Three-Eyed Raven take time out of his day to give his sister a thoughtful gift?
His powers as the Three-Eyed Raven are still a bit undefined even now in season eight, but this scene from last season seems to hint that Bran indeed is omniscient (and can see the future), as well as being able to travel back into the past. Not only did he likely see Arya slicing Littlefinger's throat not long after that moment in the Godswood, but there's also a chance he foresaw Arya going up against the Night King in that very same spot.
In the end, Arya actually gets a pep talk from the recently resurfaced Melisandre in the midst of battle, who tells Arya that it's her destiny to kill the White Walkers (They're the ones with "blue eyes," remember?). She promptly takes off running, and although we don't actually get to see how she navigates from the innards of Winterfell out to the Godswood, the Game of Thrones creators always knew that was where Arya and the Night King's showdown would take place.
Series cocreator David Benioff explained in the Behind the Episode video after "The Long Night" aired that although it hasn't been confirmed that the Night King was originally made in the Stark's particular Godswood all those years ago, the Children of the Forest did choose a very similar location to drive the dragonglass into his heart.
"We knew it had to be Valyrian steel put to the exact spot where the Child of the Forest put the dragonglass blade to create the Night King," Benioff said. "And he's uncreated by the Valyrian steel."
So, it seems there have been clues that Arya would be the one to save everyone from an eternal Winter all along. Now, all we have to figure out is if she'll also be the person to save Westeros from Cersei Lannister.