[Metathron]

I have three treasure maps from different people in the Islands of Freedom, but I can't quite work out where the places marked by X are. Actually, one is a kind of key in the form of a pyramid. Are you supposed to use it in the cemetery in Western Islands? I didn't see any way for that to work.

Any hints?

EDIT: I see that one of the maps leads to a diamond the only value of which is in selling it apparently.