Of course, the people forced to live in this area are the poorest in Horizon. They include many immigrant families who came to Horizon during and immediately after the War after being evicted from their old homes by victorious Four Kingdoms forces. Such immigrants are often distrusted by 'native' Horizon folk. Typically the slums act as a source of unskilled and semi-skilled workers for the rest of the city, although a few skilled workers of the Docks and the Steam who have fallen upon hard times also live here. Both underworld and overworld use the area as a source of dumb labour in this way. The Slums also have a few industries of their own. Horizon's stockyards and abatoirs are located here, where animals are driven in through the [?] gate and through the streets from the station. The stench of the animals and their deaths permeates the entire district, combining with the factory fumes spilling over from the Steam and the reek of sewage from the Docks to give the Slums a legendary perfume. A number of cottage industries produce cheap, badly made copies of goods that the inhabitants can't afford otherwise (but not the sort of thing that would be mass-produced, obviously the factories of the Steam take care of those). Notoriously, the Clockworker's Guild is forever launching crusades of variable violence against shoddy rip-offs of their devices from this area. Such goods get sold at the numerous small street markets in this area, alongside various illegal goods that are too low quality or too stolen to sell in the commercial district. Fences often make use of these markets. The Slums also have a lively market in various entertainments, usually illegal; this is the place to come to spectate on knife fighting or mass cruelty to animals (bear-baiting, and so on), and also for extremely cheap drink and brothels. Some of the nobles like to come here to make their own fun with the inhabitants in imaginative ways.
For the mobs of Horizon, this district is of interest for four reasons: cheap casual labour, hiding things, and selling things, and religion. As to the first, many people in the Slums are desperate and willing to undertake any job for a bit of cash. As to the second; both deeds and people can readily be concealed in the Slums, where the Watchdogs rarely tread, and people generally don't inquire after the business of others. The Imperial Government Ruins can be used to hide something where no-one will look; the Slums can be used to hide things in plain sight. Apart from Kraelings, other visitors from beyond the Wall are often housed here. As to the third, the small markets and petty crooks and trader of the slums can be used to unload goods that couldn't be sold in the commercial district. Finally, if a mobster wants to deal with cults of the various gods, the slums are the most likely place to make contact within the city.
However, there are complications to carrying out business - even illegal business - in the slums. The bewildering quantity of petty crime and random violence is part of this; the other part is the Three Families. Out in the depths of the slums, one can suddenly stumble upon large regions where the buildings become clean and well kept, the street gangs abruptly become well organised and polite, and the cult graffiti is nowhere in evidence. These are the areas in which the the Three Families mobs are the strongest; here, they have formed an alternate government that keeps its own order. In fact the Three Families are the dominant mob throughout the slums, but it is beyond even them to keep order throughout the whole huge district. Nevertheless, they keep a sharp eye on the other large mobs when they operate here, and often demand a cut of the profits in return for protection. The Families are also responsible for much of the entertainment industry here.
The other oasis of calm in the Slums is the Ghouls' quarter, the area reserved by the Mayors' Compact for the housing of the Ghouls (and the area to which the Compact restricts Ghoul dwellings). It is marked by wooden arches over the streets; on the human sides, these are typically carved and painted with lurid scenes of nightmare creatures devouring their still-screaming victims. On the Ghoul sides they are kept clean and sanded down. The buildings here are noticably sturdier and less closely packed than in the rest of the slums, and the inhabitants are generally quiet, sober and hard working. A human walking here can expect to get odd, almost hostile looks, but will not be interefered with except to be gently restrained if causing trouble in some way. The human inhabitants of the slums share some customs with the rest of the city, and they leave the Ghouls free of trouble for the most part.