[Chainsville is a home-brew setting for Wizards of the Coast's Gamma World D&D 4E RPG. It is based on Janesville, WI, where I currently reside.]
Chainsville is a small fortified town along the banks of the Rawk River. The town is sandwiched between the radioactive wilderness known as the Ur-Ban Jungle and the Wastelands - the picked over ruins of the much larger Ancient city that Chainsville is built upon. The town is named for the massive chains that have been built across the Rawk River at various points, allowing complete control of traffic along the river.
Chainsville is ruled by the Loved and Most Reasonable Emperor Norton Kane, a militaristic tyrant who inspires fear and terror in his subjects. However, he also keeps them protected from the horrors that reside in (and sometimes decide to venture out of) the Ur-Ban Jungle and the barbaric residents of the Wastelands, as well as offering a comfortable life for his army.
Kane's rule is indirectly opposed by an enigmatic figure known as Mother Mercy, a healer who oversees the Temple of Mercy and offers rest and succor to all those who need it, no questions asked. While Mother disagrees with Kane's military mindset, she does not openly speak out against him or foment rebellion. At the same time, Kane finds himself unable to move against the healer, as she provides a great service to his wounded soldiers. At the moment, the two leaders are at a stalemate, but many speculate that an open conflict is inevitable and imminent.
Before the Big Mistake, Chainsville was a city of a comparable size to the Ancient cities of Madzon, Uclare, and Luhcroz, though not as large as the nearby Ancient mega-cities of M'wahkee or She-Coggo. At the very same moment that the Big Mistake happened, a small nuclear device was detonated in a shopping mall. The explosion, combined with the forces of the Big Mistake, devastated much of the city and birthed the strangeness of the Ur-Ban Jungle. The areas southwest of the Rawk River were the least affected by the disaster, and many of the surviving populace eventually congregated there.
For decades, the area was a lawless and barbaric area. Between the abominations of the Ur-Ban Jungle and bloodthirsty mutations living in the ruins, life was often short and brutal. Then Norton Kane arrived with Ancient weapons and vehicles. In a relatively short amount of time, he built walls and offered protection from the dangers of the area. As more and more people fled to the safety he offered, he organized military scavenging parties, stripping the areas that are now known as the Wastelands of materials used to rebuild Chainsville. The famous river-chains were forged, giving Kane control over travel and trade on the Rawk.
A decade after Norton arrived, the healer now called Mother Mercy emerged from the Ur-Ban Jungle, bloodied and near death. She was taken in by Norton's guard for questioning, but after months of interrogation, it was determined that she had no memory of who she was or how she had come to be in or survive the Ur-Ban Jungle. After her emergence, Norton declared that the Ur-Ban was strictly off-limits. No expeditions would ever go in, and anything or anyone coming out would be executed on sight. This decision, and the timing, has caused many to speculate that Mother Mercy's interrogation was not entirely fruitless.
After being released and allowed to stay in Chainsville, Mother Mercy took up residence in the Ancient Temple of Mercy. The temple had been abandoned and ignored by Norton, who had no inclination toward such things. Over the decades, Mother Mercy has restored the temple to a semblance of its former glory, and has gathered a small cadres of followers, known as the Daughters of Mercy.
The fifty years since Kane's arrival have been more-or-less uneventful and lead to a new prosperity for the town. While his rule is absolute and, at times, seemingly cruel, the Emperor has brought a respite from the creatures of the Ur-Ban Jungle and the Wasteland raider, established a standard currency, and brought business and trade to the area. Chainsville is perfectly placed as a crossroads for both overland and river trade caravans from many surrounding cities. However, there are others who are interested in more than trade in the town...
The nuclear explosion during the Big Mistake and the resulting Ur-Ban Jungle make Chainsville and area of interest to the Radioactivists. While Kane has established a lockdown on travel into or out of the jungle, there are still holes in security that can be exploited by those adventurous or wealthy enough. PCs belonging to the Radioactivists might be sent to the city to find a way into the jungle to explore it. Alternately, PCs might be hired by either Kane or Mother Mercy to enter the jungle and stop a group of Radioactivists before they achieve whatever nefarious plot they have in mind.
Emporer Kane's claims of rulership extend far beyond the walls of Chainsville, though he does not currently have the military might to back these claims up. These claims might conflict with the wishes of Emperor Napoleon III and the Brotherhood of the Fit. Brotherhood characters could be sent to town to sow unrest or to try and take out Kane directly. Alternately, Kane might have need of a group of individuals to make a scouting run or strike on nearby Brotherhood encampments.
The Wastelands are not unpopulated. A strange mix of outlaws, barbarians, and hermits live beyond the western walls of Chainsville. Mother Mercy or Kane may need to find someone who has fled to the Wastelands, possibly to avoid being found altogether. Alternately, members of the Red Death or the Iron Society may have taken up residence in the Wastelands and may be looking to start a bit of genocide.