As I discussed last time, I need to determine what kind of game I would like to run in this city before I make any major decisions about it. I am discussing the genre here more than anything else. In my experience, hack-and-slash style games do not work in an urban setting. If the city is to be believable at all, there has to be some kind of rule of law, and the authorities tend to look down on murder hobos inside of the city limits. So, I can eliminate the traditional D&D-style game right off the bat. That isn’t to say that you cannot run a city game using D&D or one of its descendants, I have run D&D city campaigns in the past, most recently a City State of the Invincible Overlord game using Castles & Crusades, but they tend to have a narrow focus. The verb mix of D&D is not great for urban campaigns. While I am not making a game decision at this point, it is likely that D&D and its ilk are out.
I have a vague idea that I want this game to be science fantasy in nature, mixing magic and lost some technology. Obviously science fantasy covers a large group of possible settings, everything from Thundarr the Barbarian to Rifts falls under this umbrella. The sliding scale between science and fantasy is long and covers a lot of ground.
When I think about stories that take place in cities, I tend to think of mysteries, especially noir mysteries. I think I would like my game to have some of that feel, the recent trend in urban fantasy has shown that solving mysteries in a fantasy world can be interesting. Obviously, if I want to have mystery-solving be a large part of my game, that is going to narrow my future game choice a bit.
The other thing I want in my game is political intrigue, I want the players to be able to effect the city in large ways over time. This means I will need to detail a good number of factions and develop a way for the characters to interact with them.