If you have the Vampires Game Pack (required), this mod will let you buy the fog that is usually seen covering Forgotten Grotto. It’s layerable and available in many colors so you can create just the right effect for the party you’re throwing, adding a misty ambience.

The only hitch with this item is that it cannot be deleted. You will have to raze the lot or go back to a save point from before it was placed if you want to remove it.