That dagger is 300 years of plot armor and no one realized it until HOTD. For those who don't know: That little Valyrian steel toothpick is Aegon the Conqueror's dagger. The first Targaryen king had it made. On the blade it says in High Valyrian: "From my blood comes the Prince That Was Promised and his will be the Song of Ice and Fire." Aegon had a dream. He saw the Long Night coming. The dead in the North ending the world. He conquered Westeros not because he wanted a throne - because he needed to unite the realm to survive the dead. He carved his prophecy ON THAT DAGGER. 300 years later: - It tries to kill Bran in Season 1 (starts the War of the 5 Kings) - Littlefinger owns it - Bran gives it to Arya - Arya uses it to kill the Night King The prophecy was real. "From my blood comes the Prince That Was Promised." Arya is not Targaryen blood. But she was given the dagger by a Stark, who was given it by a Targaryen (Aegon -> Visenya -> ... -> Rhaenyra -> ??? -> Bran). The blood path holds. The dagger didn't just fulfill the prophecy. It WAS the prophecy. Aegon literally forged the weapon that would save the world. That's why when Rhaenyra holds it in HOTD and says "It's all we have" - she's holding Chekhov's gun.