The "Urns of Old" are for decorative use only...or for confusing gamers who think that they're targetable. They fall in the same class as the useless "demonic figurine" in Skull Castle" or the "Pile of Sand" just outside the Anephas Shrine. Just ignore them.
The Voodoo dolls cast some sort of spell at an opponent when you invoke them (Curse, Enfeeble)? I've never used them before, so you may try it out and see what it does.
-Sazerac