So, I'm building a city for a game and I need some help coming up with ideas.

I have the basic outline. The city was originally built on the site of the ruined capital of a long-gone empire of fey. It was originally full of spirits, magical phenomena and powerful magics, but those have, for the most part, been looted and sold. Still, the founding populations of the city for a long time were exiles, mercenaries, adventurers and traders and that is reflected in the culture. As time went on, it became a haven for political, religious and magical exiles as well and though it is currently tenuously controlled by a powerful Empire, that Empire is across the sea and travel is long and dangerous, so they still come here.

What I'd like is a few ideas for the kind of people and groups who might end up here. Also, demon binders and necromancers are just a bit played out, so I'd also like a few more original ideas for magics that might be forbidden in an Empire vaguely modelled on the early Roman Empire. Relatively religiously and politically tolerant, as long as the Imperial institutions are respected, the Emperor is worshipped and taxes are paid.

A few ideas are pretty standard, of course. Several mercenary companies, including some founded by disgraced noble families who had to flee from the heartland of the Empire. Then, we have the slightly more unusual one:

A cult that recruits amongst the lowest classes, especially slaves, miners and the urban underclass and previously lead to unrest, before being declared illegal.

A cult of soul binders who claim that they can bring back and channel the spirits of long-dead heroes of the Empire. This is seen as incredibly disrespectful to the ancestors by most of the Empire, even if the effects can be quite powerful. Priests would bind the spirits of powerful generals or warriors to themselves and use their skills and knowledge.

What else?