Found on the corpse of a Death Knight dangling off a ledge in a somewhat hidden room, which is guarded by a Catacomb Conjurer.
The room can be found after the first stone elevator (not counting the elevator between the entrance of the catacombs and its site of grace).
Once at the bottom of the elevator, there will be large open room with a staired balcony on the eastern walls. Follow this balcony while keeping an eye on the guard rail, past the lionheaded imp until the path turns to the right. There will be an opening in the in the corner of the rail. This opening will lead to a drop down to a small ledge that'll immediately lead this hidden room.
