This is it...
The year is 2137, 50 years after all previously established civilizations collapsed. Many people suffer from a disease, Crysol, that causes crystals to form over the afflicted and spread as the virus reaches advanced stages. As the crystals spread, the host's body is rendered significantly useless and immobile. The disease has 4 stages.
1st stage: It has a 50/50 chance of being benign. The inflicted suffer from dizzy spells or delusions. They are capable of most movement tough the afflicted area is significantly weaker and easily strained. Crystals have begun to form in a concentrated area although contained in one area.
2nd stage: The infected suffer symtoms of schizophrenia and tend to suffer from "visions" and hearing voices. This stage is the last stage that is possible to entirely treat the disease. Crystals maybe become more concentrated in the infected area or the infection might spread to other limbs.
3rd stage: Although not entirely immobile, their senses may become morphed and distorted as they begin to suffer from memory loss.
4th stage: vital organs begin to shut down. Usually 90% of the body has been rendered immobile. This stage is commonly fatal and infected will often die unless put under proper treatment.
The disease is not contagious by contact, although if a crystal manages to breach a persons body, there is a chance they will catch the disease.
There are those who survived the first stage of the disease and and also those who gained a immunity to the disease, known as The Outcasts, and respectively outcasts from society due to gaining abnormal abitlities consisting of being physically stronger, durable, and advanced reflexes and some gained unique abilities such as flight, advanced intelligence and various others.
Maybe people, Outcasts and infected, have attempted to blend into noarmal society. Both have been discriminated by society, Outcasts more than infected. Outcasts became bandits , some bold enough to raid towns. Soon mercenaries to counter bandits arose, although significantly outnumbered by the thieves.