It's the staff. And if you used the Search option you would know this without having to add yet ANOTHER post about the subject.

in skull castle i can't find the object needed to get into mabbi whateverhernameis's room
i've gotten the two bone keys, and the key from the lich, i've gotten the relic and given it to the lich and gotten his staff. spent the last week wandering around that dumb castle looking for buttons, switches or anything that would let me into a new area but the only place i can see that i haven't been to is the room where the head vampire is. also, what is the idol supposed to do in the room with the lava pedastel (sp).
any help would be greatly appreciated, really don't want to go on to the next section of the game without fully completeing this one.