These mysteriously-crafted alchemical poisons are designed to affect elementals and made only by the most capable of alchemists . When an elemental is subjected to one of these poisons, the poison affects the elemental as if it didn't have any immunity or resistance to poison or the poisoned condition.

Each poison is applied to a weapon -- one dose can coat one weapon or piece of ammunition. Applying the poison takes 1 minute. A creature that takes slashing or piercing damage from a weapon or pierce of ammunition coated with the poison is subjected to its effects.

Extinguishing Foam (Injury). A creature subjected to this gray poison must make a DC 18 Constitution saving throw, taking 35 (10d6) poison damage on a failed save, or half as much damage on a successful one. Fire elementals have disadvantage on the saving throw, and when a fire elemental fails the saving throw, any fire damage it deals for the next 1 minute is halved, and its speed is halved for the same duration. It repeats the saving throw at the end of each of its turns, ending the effect on a success.