Danger abounds in a variety of forms throughout A Sundered World. The Bahamut Span is the territory of the tarchons, a race of violent warriors that are thankfully usually embroiled in combat against each other. The Maelstrom is a chaotic realm of cyclical creation and destruction. It's easy to avoid, but contains valuable elemental cores and is a rich source of raw materials.
The Iron Circle is no less dangerous, just more subtle, and it is because of that that many would argue that it's in fact more dangerous. It is home to the charming, cunning, and cruel devils and cambions. The capital of this literally hellish realm is the city of Asmodeus, built upon and within the petrified corpse of its namesake, which is in turn chained to a great iron sphere that contains the nine circles of hell.
Here's a WIP to give you an idea as to what it looks like (which I think is much improved over my initial sketch, made over three years ago):
Though the absolute authority is the Word of Asmodeus, most of the city matters are overseen by the Nine, who each rule their own circle of Hell, and their agents.
Devils of all types roam the streets and skies, looking for any opportunity to gain power and station, though everyone is cordially welcome. If you find yourself with the unfortunate necessity to visit, you would do well to purchase a writ of passage as soon as possible, lest you fall prey to claw or contract.
Black barges deliver a constant stream of souls to the city. Some are transformed into new devils, but most are reduced to a larval state and sold as fuel, food, and/or labor.
Though souls are the most important part of the Iron Circle's economy, the foolish and desperate can find nearly anything they can dream of among the twisted spires and wails of the damned. For the right price might even be able to attain it, and if they are truly fortunate, they might even live long enough to at least somewhat appreciate it.
Here are a couple pages from the cambion race:
When you make a cambion, you get to choose a sin and gain a move. When you level up, you can opt to choose a move from your class, or further steep yourself in sin. For example, there's an advanced move for greed that gives you a potent bite attack, and another that gives you a kicker effect whenever you gain something valuable.