There have been rumors of malistares tomb in the necropolis, I had a search of my own they said it would be accessible after you beat malistare. I have not beaten malistare yet but I found that there are 11 possible areas in the necropolis. If you know anything about this I would be happy to know.
I have never heard of Malistaire's tomb, but I have heard of and beaten Sylvia Drake's tomb. Not sure if I helped, but I hope I have. Finnigan Shadowglade, Level 47 Conjurer