The Valyrian Steel dagger known as the Catspaw Dagger has played a key role in Game of Thrones Season 7. Because it’s been featured so prominently, both in the most recent episode and in promotional photos before the premiere, it almost certainly has a greater significance, and it all boils down to one thing: That dagger is Targaryen as hell. It might even predict where the books and show will diverge.

The dagger was first used in Season 1 to try to kill Bran. It then passed from Catelyn Stark to Ned Stark before eventually ending up in Littlefinger’s little fingers. In Season 7, an illustration of the dagger appeared in Sam’s book in the Citadel. In “The Spoils of War,” Littlefinger gives it to Bran, who in turn gives it to Arya. So what’s up with this dagger and why is it connected to House Targaryen?

The Targaryens have always been the most mystical of Game of Thrones houses for good reason. These beautiful, dragon-riding people ruled the Seven Kingdom hundreds of years but now there’s tragically just one left (or so everyone thinks). Their castle also happens to sit on a mountain of Dragonglass — which adorns the handle of the dagger, and they have a taste for Valyrian Steel weapons like Dark Sister. Sam was reading a book about Dragonstone when he saw the illustration of the dagger, so it’s clearly a Targaryen weapon. To understand why that might be important, let’s talk about another Valyrian Steel weapon owned by the Targaryens: Dark sister.

The imposingly named Valyrian Steel sword was wielded by Visenya Targaryen, who Arya proclaimed her admiration for in her Season 2 chats with Tywin Lannister. Visenya is Aegon the Conqueror’s sister-wife. Unbeknownst to Arya, she’s also Jon’s ancestor.

Dark Sister was lost during the Blackfyre Rebellion, which hasn’t really been mentioned on the show. The show would need to find a way to introduce the blade and unload all that backstory via exposition if Dark Sister were to appear, and that would eat up valuable screen time in the nine remaining episodes. It’s the same reason Euron Greyjoy is different in the show and the books — there’s no time to explain all of his oddities if he appeared the way he does in the books.

But one Reddit user has the intriguing theory that the dagger helps predict where George R.R. Martin’s unpublished final two books are going: Arya is going to fight the White Walkers with the Valyrian Steel sword Dark Sister.

As they explain, the dagger is a stand-in for Dark Sister, which Arya will use to fight the White Walkers in the books. In the show, since the dagger is more immediately recognizable and doesn’t require exposition, she’ll use that to fight them instead.

Fans also theorize that if Jon Snow’s father Rhaegar Targaryen finally appears in Bran Stark’s visions in Season 7, he might have the dagger. It’s a Targayen ancestral possession — and both dagger and House Targaryen have important roles to play in the war to come. It could very well be the weapon used to kill the Night King.

Game of Thrones Season 7 is currently airing Sunday nights on HBO.

Photos via HBO