The heroes find a small crypt somewhere and being brave adventurers they want to check it for evil forces (=graverobbing). Or for any other reason.
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...