Game Of Thrones Season 7 Premiere: 9 Things You Might've Missed In 'Dragonstone'
3. The Catspaw Dagger

Way back in Season 1, when Bran was lying crippled in his bed, the 'catspaw assassin' came to murder him, before himself being killed by Summer after a brief struggle with Catelyn Stark.
The weapon he used was a dagger made of Valyrian steel, and Littlefinger managed to convince Catelyn the blame belonged on Tyrion. The last we know, it was Baelish himself in possession of the dagger.
This week, when Sam is browsing through books in a Citadel, he flicks past a page that has the very same weapon pictured on it. This would suggest it's a very old Targaryen blade (given this is the same book that reveals dragonglass under Dragonstone), and there's a good chance it's inclusion here is foreshadowing its return: it appears as though Arya has the blade in EW's promo shots:
Also in that book, Sam skims past a page making reference to ingesting dragonglass as a cure for illnesses and disease, which could well be a hint towards how Jorah Mormont will be saved from greyscale.