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.
For those familiar with cantrips, you know they are minor acts of magic that have hardly any noticable effect on the world. For example a cantrip to make your food taste better won't heal you any more, or be any more nourishing, just won't make it so hard to get it down. A light cantrip certainly won't be able to blind or even distract anybody, but you might be able flash it to signal someone looking at the right spot.
What if children's nusery ryhmes were a form of cantrip? Like the "Rain, Rain, go away, come again another day." One child singing it wouldn't do more than spare her house a couple raindrops, but what if the whole village got together and was chanting in unison? Each one doing just a bit might actually be able to divert a whole storm...