sorry this reply took so long...damn migraines (2wks worth every month)

NE-Way...here's something I found...
Just pull every lever u can. If u r stuck at the resting place, enter through the Gehena. The one sigil you cannot find is in the Lava Pit! No you didnt get it. Jump onto the moving platform. Keep facing the wall that has the door from which you entered from. There will be an opening past the door which you can see. there is the sigil. if you dont understand. just jump onto the moving platform, and look around. its there.

I'll look for more IF u need it w/my luck, u've already figured this one out and are well on u'r way...wavers!