Each time the Fog appeared in the Shadow Valley, it would hang around for at least a week, and sometimes for as long as a month.
During that period, the valley would turn into a living nightmare.
Mysterious deaths would occur, and by the time the Fog lifted, the valley would be littered with corpses, each one twisted and mangled in unspeakable ways. It was like looking at a Christmas tree, but instead of twinkling lights and shiny ornaments, the valley would be decorated with the lifeless bodies of its inhabitants, and it happened every single time.
Today, when the Fog rolled into Shadow Valley, its inhabitants, the beasts and the devils, knew what to expect as they'd been through this before, but that didn't make it any less horrifying.
They were scared, really scared, because they were aware that they could be the next victim of the Fog, dying a horrifying death without knowing what killed them.