Dust of Dryness

This small vial contains 1d6+4 pinches of dust. You can use an action to spread a pinch over water, transforming a 15-foot cube of water into a small pellet that weighs less than an ounce. 

Using an action, you or another creature can break the pellet against any hard surface, releasing all of the water and destroying the pellet. 

A creature composed mostly of water that is exposed to a pinch of the dust makes a DC 13 Constitution saving throw , taking 10d6 necrotic damage on a failure, or half damage on a success.