In Game of Thrones season 7, episode 4, “The Spoils of War,” a particular dagger makes a reappearance after six seasons. Made of Valyrian steel and once wielded by an assassin sent to kill the recently injured Bran Stark in season 1, the knife shows up in Littlefinger’s hands as he gives it to Bran in an apparent attempt to forge a bond between them. Bran, who has no practical use for the dagger as the Three-Eyed Raven, bequeathes it to Arya, who wields it well in a spar against Brienne of Tarth.
In season 1, the assassination attempt on Bran, and the subsequent suspicion Littlefinger places on Tyrion Lannister for being behind the attempt, helps trigger the war between House Stark and House Lannister, which was likely Littlefinger’s aim. (Chaos, after all, is a ladder that provides opportunities for ambitious men, as Littlefinger once told Varys — a quote Bran throws back in his face, as a hint that he’s seen more of Littlefinger’s behavior than any double-dealing schemer could want.) While the show hasn’t explored who’s truly behind the assassination attempt, in George R.R. Martin’s novels, Tyrion later hypothesizes that Joffrey was behind it for some fairly elaborate and not entirely convincing reasons. Since Joffrey and Catelyn are already dead, it’s unlikely the show will revisit this exact tidbit. However, Littlefinger does openly tell Bran that he doesn’t know who the dagger belonged to before the assassination attempt, opening up the possibility of different revelations about who may have been involved in the attempt on Bran’s life.
In the show’s version of events, the dagger last appeared in Catelyn Stark’s hands as she tried to find who was responsible for the assassination attempt. But after she died at the Red Wedding, the dagger disappeared. Perhaps Littlefinger went through Catelyn’s things? Or visited her remains? He’s certainly not lacking in unsavory means to acquire what he wants.
As Littlefinger passes the notorious blade to Bran, he mentions another, less intriguing dagger: the anonymous one used to cut Catelyn’s throat during the Red Wedding. He wanted to stop that one, he says. So why remind Bran of his failures to protect either Bran or his mother? Valyrian steel is valuable, but it’s still an awfully strange present. Still, it’s worth noting that Valyrian steel can kill White Walkers, and now Arya has a weapon in her hands that’s certainly going to turn up again in a significant way at some point in the series.