This small packet contains 1d6 + 4 pinches of dust. As a Utilize action, you can sprinkle a pinch of the dust over water, turning up to a 15-foot Cube of water into one marble-sized pellet, which floats or rests near where the dust was sprinkled. The pellet’s weight is negligible. A creature can take a Utilize action to smash the pellet against a hard surface, causing the pellet to shatter and release the water the dust absorbed. Doing so destroys the pellet and ends its magic.
As a Utilize action, you can sprinkle a pinch of the dust on an Elemental within 5 feet of yourself that is composed mostly of water (such as a Water Elemental). Such a creature exposed to a pinch of the dust makes a DC 13 Constitution saving throw, taking 10d6 Necrotic damage on a failed save or half as much damage on a successful one.
Pinch absorbs 15-ft cube of water (becomes pellet).
RollQuest ships the D&D 2024 SRD as a content pack, on a 5e character sheet that does the maths - roll from the sheet and let the numbers work themselves out. Free to start.