The Black Knifeprint is a Key Item in Elden Ring that can be used to progress two separate questlines. Namely, Sorcerer Rogier’s questline and Fia’s questline.

The quest item drops from the Black Knife Assassin (Black Knife Catacombs) in the Black Knife Catacombs. You’ll find the assassin hiding behind an illusory wall in the room leading down to the flooded pit.

Players can find the catacombs in the northeastern part of Liurnia of the Lakes. Start at the Ruined Labyrinth Site of Grace and make your way northeast past the Minor Erdtree (Liurnia Northeast). To enter the catacombs you’ll need to defeat or sneak past the Mausoleum Knight that’s guarding the entrance.

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After learning about the Black Knifeprint from Sorcerer Rogier you’ll need to talk to Fia to find out the item’s location. Alternatively, you go straight to the Black Knife Catacombs and collect it from there without first talking to Fia.