There are fifteen treasures, each of which exist in both the light and dark portions of a level. However you only need to find one of those two versions. Fake walls hide all of them, which can be found because they do not reflect sound and do not allow you to see any sound passing through them. Once obtained, a treasure remains if you die or do not complete the level. It will no longer appear at its light or dark locations. The following are the locations of the treasures in each of the dark levels.

VI (6) "Calm"
Press the second button and open the final door towards the exit, then return to the start of the level. A third button will now appear where you started. Push it to open a door leading to the left. Go to the end of the hallway enter the fake wall to find the treasure.

XIII (13) "Witness"
Wait silently at the edge of the room with the red orb. It will do shift back and forth five times before disappearing. Once it is gone, walk across the room to the left then move up when you hit the wall. You will find a notch in the slanted wall which has a small fake wall at the back. Walk into it to find the treasure.

XIV (14) "Interlock"
At the end of the right side path you will see a drip with some faint blue behind a fake wall. Trick the red orb out of the area to allow you to drop into the water without being attacked. Swim to the end to find the treasure.

XIX (19) "Distraction"
Just before the exit is a portion of a yellow button visible from under a fake wall. Step into the wall and press it. You will see the far right hallway extend, and the red orb move slightly into it. Trick the red orb back to the exit side. This is more difficult than going the other way due to the small tunnel's shape and the slight movement of the orb. Walk around to the end of the now extended hallway to find the treasure.

XX (20) "Projection"
After reaching the large room before the exit, notice the strange apparently unreachable room down and to the right. Feel along the right wall in that direction to find a fake wall. Follow it along the hallway it hides and enter that strange room. The right wall of this room is also fake. Pass into it and move up. Keep travelling up past the exit into yet a third fake wall to find the treasure.

XXII (22) "Taunt"
Get the red orb out of your way then enter the middle of the upper wall, evenly between the two drips into the water to find a fake wall. Follow it up. At the very end of the hallway is the treasure.

XXIV (24) "Eliminate"
After passing the part that snakes up and down, there will be a drop of blue under a fake wall before the hallway with red on both sides. Enter it to get the treasure. You will most likely die afterwards.

XXVI (26) "Timing"
Get to the end, but do not use the exit. Get close to the moving block in the middle of the last room from the exit side. You can find a fake wall below the moving block. When it moves away, enter and collect the treasure.

XXVII (27) "Consequence"
After passing the second moving block, you will find be a fake wall against it on the wall to the right. Follow it down to find the treasure.

XXVIII (28) "Thrust"
After getting pushed down dangerous hallways twice, during the third time notice that you are being be pushed slower. Do not take the first exit found on the right. Instead, continue straight and move to the small portion of safe landing down and slightly to the left. Go all the way down and through the fake wall at the bottom to find the treasure.

XXIX (29) "Crush"
When reach the second crusher, get to the exact middle to find a small slit on the top crusher plate. It is just large enough for you to enter. Do so, then move up through the fake wall to find the treasure.

XXXI (31) "Exposure"
After activating all four plates, do not go to the exit. Instead, return to where you started the level at the lower left and reenter the small hallway. You will find that it is now longer due to a fake wall. Pass through it and find the treasure.

XXXII (32) "Ambush"
After breaking a wall down and reaching the top area, you can find a fake wall on the top point of the triangle wall configuration. Enter it and hit the button to open another fake wall at the lower left of the triangle that can be found. While avoiding the red orbs, sneak back around to a new fake wall. Enter it to find the treasure.

XXXIII (33) "Guardians"
Activate both buttons on the top and bottom of the water channel. Be very cautious of the red orbs when entering and leaving the water. Afterwards, return to the start of the level to find that a small red-lined path has now appeared. Carefully cross it and enter the fake wall at the end to find the treasure. Note: You do not have to use either of the buttons if you just want to complete the level.

XXXIX (39) "Apparatus"
En route to the exit, remain at the bottom while you move to the right. Follow that wall to eventually find a fake wall at the lower right corner of the level. Enter and follow it to find the treasure.