This is a missable achievement as there is a narrow window in which you can get this achievement without having to restart the game. After you get the arbalest from the crypt you need to head to the culling grounds (the arena near where you first enter the game). The door to the balcony section has a lock above the door that has to be blasted with the arbalest, then an activation/key sphere placed into it using your glove powers. DO NOT PLACE THE SPHERE IN THE LOCK.
To get the trophy, you need to blast open the lock with the arbalest and then pick up one of the Hermites wandering in the area and toss it into the lock. Once it's in there for a few seconds the achievement should unlock. Once you put the sphere into the lock, you cannot get this achievement.