On the season premiere, the Valyrian steel blade used in Bran's assassination attempt was shown in one of Sam's stolen Citadel books.

The "catspaw" blade might be an ancient Targaryen dagger. HBO

Sam stole several books from the Citadel library's restricted section. And while he was flipping through the pages, we got a peek at a drawing of a very important weapon.

The dagger is often referred to as the "catspaw blade" — a reference to the would-be killer (or catspaw) who tried to kill Bran on season one. We knew the blade was made from Valyrian steel and had a hilt made of "dragonbone," but its origins have been a big mystery in the books and the show.

Based on Sam's book, it looks like we now know the blade is an ancient Targaryen weapon.