Deadguy said:
One more quick question though: to what extent is the nature of the city determined by its locale? Is it very tied into its physical location (I note the reference to the volcano)? In other words, how much of it surroundings would I really need to port over to avoid changing the place and its history too much?
I'd say in order to get the most use out of the city, you should account for the following:
1) Hollowfaust arose because several powerful necromancers traveled to a ruined city where there was lots of death energy — essentially, where practically the whole city died at once, thus creating an important site for research into necromancy. In this case, it's a Pompeii-style volcanic eruption that killed the city. You can choose something else, but the presumption is "ruined city that died all at once."
2) The city became a city, and not just a tiny enclave, because it accepted a flood of refugees. You should probably account for what these refugees were fleeing, where they came from, and why they accepted the necromancers' rule as preferable to what they could have gotten elsewhere. (The other reasons for citizens to live in the city rather than anywhere else, such as primo sanitation and a considerably low crime rate, aren't reliant on locale at all.) The city has also withstood several sieges from hostiles, which you may or may not want to duplicate depending on where you slot it, but they do give the citizenry added reason to be happy where they are, so it's another consideration.
3) This is kind of optional, but the volcano also provides a distinct physical separation between where the necromancers live and where the ordinary citizens live (it's full of chambers, passages and vaults where the labs and undead storage facilities — ah, barracks are placed). The necromancers don't live directly among the citizenry, which changes the tone a bit. You might want to think about another physical feature like that which could be used to separate Guilds business from city business.
Those are the things I'd strongly consider porting over; everything else is pretty darn mutable. IMO, natch.