As an action, you can create a packet of dust. A creature can use an action to sprinkle a pinch of it over water. The dust turns a sphere of water into one marble-sized pellet, which floats or rests near where the dust was sprinkled. The pellet’s weight is negligible.
Someone can use an action to smash the pellet against a hard surface, causing the pellet to shatter and release the water the dust absorbed. Doing so ends that pellet’s magic.
An elemental composed mostly of water that is exposed to a pinch of the dust must make a Fortitude saving throw, taking 4d6 necrotic damage on a failed save, or half as much damage on a successful one.
You can increase the damage by 3d6 for each additional catalyst expended.