Navigate the Vault is an objective in Duality.
- Once in here, go to the far side of the large thing in the middle.
- Look to the left-hand side to find a bell through some grating.
- Be sure you are standing on the walkway with the treasure on either side of you.
- Shoot the bell to be taken to the Nightmare.
- Getting into the Nightmare, you will immediately need to deal with a few Warbeasts as well as a Centurion.
- Clear them to have some space to work.
- Head back toward the large object under the cloth.
- Look to the same side as the bell, you will see narrow walkways above the void.
- Long Jump out toward the narrow walkway, run along it, toward the high walkway.
- Go to the right-hand edge of this higher walkway.
- Jump through the opening on the right.
- Land in the hallway through the opening and head over to the right.
- Go back toward the grating to reach the bell you used to cross over.
- Shoot the bell within the circle to return to Reality.
- Once there, look for the opening close to the ceiling, to the right.
- Jump into the opening and run along it.
- This will lead to an up-ramp.
- Run up this ramp to reach the top.
- At the top, turn around and jump for the ledge just behind you.
- Land here, turn around, and then jump up to the next ledge.
- Landing there, jump up to the area just above you.
- Look through the grating to the grating on the far side of the room you are now in.
- There, you can just see another Bell.
- Get the bell to strike by shooting it to be taken into the Nightmare.
- Inside the Nightmare, start out onto the narrow walkway in front of you.
- Get across the wide room using the walkways to reach the Bell.
- Shoot the bell while you are within the circle to return to Reality.
- Back in Reality, go to the far side of the bell and look upwards to find a ledge.
- Jump up to it and then go back toward the gap using the ledge above you.
- Look to the right to spot the narrow walkways here with a number of Cabal on them.
- Either snipe them from a distance or just run through, going for the back left hallway opening.
- Inside this hallway, run to the mid-height wall.
- Jump over the wall and then drop into the next angled shaft.
- Jump periodically to keep control of your momentum.
- This will bring you into another hallway.
- Turn to the right here.