I don't really remember where I got it but I had the idea for a campaign that had a setting heavily inspired by S.T.A.L.K.E.R. and a 'plot' heavily inspired by Final Fantasy Crystal Chronicles.
No one quite remembers how it all started, all they know is whats up in the here and now. The miasma covers the land for as far as anyone knows. To be death would be merciful of the menace, it corrupts and changes its victims into monsters that haunt and kill. Machines of yore keep the miasma at bay, these miraculous beacons of hope are the centers of settlements. But the machines are not perfect and require a power supply. Caravans are sent to travel the no man's land for the dungeons that hold the secrets of repowering the machines (old underground lab complexes). The caravans gain safe passage from the miasma by way of docile mutants that look unchanged except for strange burn marks. The miasma clears in the presence of these people but their almost comatose nature leaves them in need of protection. They have ties to the machines of yore and know how to operate them.
I would use Dark Heresy for it myself, corruption points for the miasma radiation