A wagon lays overturned on the forest road, bodies savaged by tooth and claw lay strewn about it, their weapons clean of blood, seemingly unused.
A lone man runs from an unseen threat, deeper into the forest, away from the grisly scene in the road. He stumbles, his foot having caught on a root. He lands hard, his lungs feel like lead. Panting, he comes to his knees. Two eyes of emerald light meet his, a low growl emanates from the beast, and his death is swift.
A little way up the narrow valley, before they reach the woods, the PCs notice the squat, tumbledown buildings by the riverside. They are hardly big enough for a human to stand in, and the complex cogs and shafts that occupy the central cavity of one of the buildings are perplexing. What were these buildings? And how safe are they to explore?
Alternatively a desolate place is the perfect setting for a derelict chapel or croft. There needn't be any actual physical encounter involved, but it adds atmosphere to a place to see its dead history. For instance, in the Outer Hebrides there are whole deserted villages which were razed to the ground by the English during the Clearances. Such stories give a setting authenticity and character.