I promised some thoughts on Crossgate History and the Temple District.
Crossgate History
Basically, I want to try and explain why I think Crossgate has to be a minor provincial town. The logic is like this:
The gangs control Crossgate, but they don't rule. There's a mayor and a city guard not under the control of the gangs. Now, if crossgate were an independent city state or the capital of a nation, I think the gangs would have used their dominance to seize power, and the gang leaders would all be the heads of noble houses. So I think there has to be some massively powerful external force that keeps the gangs from getting over-ambitious. So I think the city is part of a kingdom or empire. Let's say Empire.
Now if Crossgate was close to the center of government, I think someone would have sent in the military by now. Having an ongoing font of civil disorder at the heart of the empire is a political liability. And if it was distant but still important, I think someone would have send a legion by now, if only to stop the city falling into enemy hands. So I think it has to be distant and considered to be of low importance for the gangs to be tolerated.
I don't think this was alway the case, however. Someone went to the trouble to build a fortress there, so I suspect that at one time someone was concerned about the possibility of invasion. Possibly by some extra-dimensional force. Whatever the case though, I don't think anyone gives much creedence to that idea these days.
Let me take a stab on giving a possible history that could explan Crossgate. Lets say that this Empire was very magically powerful and has always been fuled by conquest. After conquoring as much of the world as the Empire could reasonably hold (areas outside of the Empire are just too tough to make it worth conquoring) the Empire looked towards magic to provide new lands to conquor.
Crossgate has always been a place where the barrier between worlds has been weak. Traditionally, a large number of demon summoners have come from here. Crossgate was origionally founded as a mages collage with the Empire's military having a strong presence. Experiments in breaching other dimensions went on for decades before a process was developed to create a stable portal into other dimensions which was large enough for an entire Legion to invade, or to perform trade.
Unfortunately the experiments have rendered the dimensional barrier around Crossgate unstable. The Empire decided to pull the Collage and the portal to the capital where they could keep a closer watch on it and directly benifit from both. The Empire kept a full garrison at Crossgate initially to prevent the unstable portals from becomming a threat to the rest of the Empire. However, after the machinery used by the Collage were removed from Crossgate the unstable portals begain to subside and were reduced to the level of a nuicence. With the Empire committed to invading other dimensions the local garrison has been reduced to little more than a police force.
While the unstable portals arn't worth the full attention of the Empire, the items and people that come through them are highly prized in many cities of the Empire. The less savory elements of the Empire were drawn to Crossgate like a moth to a flame. Gangs sprang up with each of them claiming areas of the city as their territory. At first the Govenor tried to keep the illegal activites in check, but soon realized that he wouldn't have the men nesessary to do so. Instead he chose to pit the gangs against each other only using his soliders to raid gangs occasionally when he feels they have lost respect for the Empire or threaten his power.
Over time the item trade diminished as larger supplies of cross-dimensional goods were made available through legitimate sources. This lead to the main source of income for the gangs to decline. Instead the gangs started to market exotic slaves. Crossgate itself started to gain a reputation of having excellent brothels with exotic beauties from other dimensions. Nobels and other wealthy merchants and soldiers from other cities come to Crossgate to sample the girls for themselves.
Brothels are now an established part of the Crossgate culture. The gangs act as a first line defense against whatever may come through the portals. With the gangs running the brothels and them in turn being dependent on tourists for business they tend to act low key as far as outsiders go. That doesn't stop them from fighting in the streets, but it does stop them from challenging the rulers of the city directly.
The catacombs themselves are a byproduct of the last set of magical research. Some of the areas are where the machines that provided the stable portal were housed. Those areas themselves were strengthened and made stable in a sort of between worlds space. The brothel we as players own happens to have access in its basement to one of these rooms. The farther you travel from this room the less stable the underground area becomes. Our father managed to get some of the old research notes and was able to convince a retired wizard to make a few "beacons" that allow someone wandering the catacombs to find their way back.
Anyways, hope DocClox finds something in here he can use.