Popping Pebbles

About 10 pebbles in a small bag. The pebbles are the size of a pea when inactive. Whisper "pip-pop" to make them start, "poppit stop" to make them quiet down and roll back into the bag. Command them to start and they will roll out of the bag, grow randomly in size and start bouncing everywhere.

The popping sound of the pebbles is far from silent. If someone is in the area of the bouncing pebbles, they take 1d4 HP of damage per round.