When trying to get the second Sigil in Gehenna, instead of trying to balance on the wall to cross the room, just pull the switch to raise the wall sections. Then, wait near the switch for the walls to descend. While the wall is descending, wait for it to be low enough to jump on and quickly jump to the higher platform. Pull the switch there to raise a ladder, then use this ladder after pulling the switch again to get the second Cadeaux.

Use the following trick in the Gehenna Sigil chambers where the thin platforms (walls) rise and you have only 20 seconds to do it. Pull the lever to make the walls rise, then go up the ladder. Walk on the ledge to the first alcove with the Cadeaux in it. Take your time. When you get it, go back to the lever. Pull the lever and take five to six steps backwards align Shadow Man with the wall near the lever. When the walls start to descend, get ready. When the walls reach Shadow Man's height, run and jump then jump again. You will be able to grab on the ledge. Pull yourself up then pull the lever to make the ladder appear. Then, go back down again and pull the lever to make the walls rise again. Go up the new ladder and walk to the second alcove. Jump and grab the second Cadeaux. The same thing is done for the next level with rising walls (platforms).