Source: Dungeon Master's Guide

Wondrous item, uncommon

Found in a small container, this powder resembles very fine sand. It appears to be Dust of Disappearance , and an Identify spell reveals it to be such. There is enough of it for one use.

When you use an action to throw a handful of the dust into the air, you and each creature that needs to breathe within 30 feet of you must succeed on a DC 15 Constitution saving throw or become unable to breathe, while sneezing uncontrollably. A creature affected in this way is incapacitated and suffocating. As long as it is conscious, a creature can repeat the saving throw at the end of each of its turns, ending the effect on it on a success. The Lesser Restoration spell can also end the effect on a creature.