I read alot of faqs that said you should eliminate all the mummies that basically overrun you when you take the grail cup. That is the hard way and seemingly impossible, a much better way is to use the shadow potion, walk up and take the grail. The next part is kinda tricky and can probably be done a few different ways. First way is the way i did it because i dont have any detect trap skill. So take the shadow potion and then the grail cup. You must walk slowly when getting zapped by the traps, it also helps to have alot of hp's and medicine bottles, the red ones. Now as you move along and getting zapped, hug the right side of the wall and when you will notice the main bosses figure in the shadows, walk around him. If you get too close to him as a warrior or weapon wielder you will attack him and reveal yourself.(remember to take potions as needed when you get zapped.) Now once you get around him keep walking slowly to the doorway and then you're home free. Alternately you could attempt to attack all of them, but you'll probably fail. Again alternately follow the steps above, if you can use detect trap, although never tried that so you might get detected. This is much esier than trying to fight 30-40 monsters at once.