Dust of Dryness

This packet contains 1d6 + 4 pinches of dust.
You can use an action to sprinkle a pinch of it
over water. The dust turns a cube of water 15 ft.
on a side into one pellet, which floats or rests
near where sprinkled. Use an action to smash
the pellet against a hard surface, causing it to
shatter and release the water, ending the magic.
An elemental composed mostly of water that is
exposed to the dust must make a DC 13 Con save
taking 10d6 necrotic dmg on a failed save, or half
as much on a success