Jump to this ledge and proceed through the path. Move to the other side of the stairs, and you will see a small ledge in which you can jump to. Return back to the location of the large door you opened before fighting the First Warden. This item is the Northern Monastery Wing Door.
At a certain point, you can jump onto a ledge in front of the statue to pick up at item. After the first boss fight against the First Warden, continue down the stairs of the next section that wrap around the large statue.
