The Black Marsh is a major swampland in Generation V which is only a short distance from the spawn ruins. Along with being a location often passed by travelers, the marsh is adjacent to the Broberian Forest, which hosts the major faction USBR.
The area is often avoided by passersby and occasional travellers, due to the strange disease that rules the swamp. An awful plague, belived to come from the Nether itself, infects anyone who spends too much time in these wasted lands. Only the foolish will test the truth of this.
The swamp people, living and working off of its resources are not welcoming to strangers, although peaceful unless provoked. There is a very small number of them however, due to this plague taking its large toll on the population. Many factions offered to help with the disease of the Blackmash swamps, but the natives politely declined, describing the disease is not something bad, but as "a blessing, not a curse". Noone yet knows the swamp people have this attitude towards the disease that's killing them, and we doubt we ever will, the swamp people don't like to talk about it much, anyway.
Because of this harsh environment, and its locals, no faction has yet called this place its home. But everyone understands why; there's no room in this swamp for the even worse disease of human scum...