From Lost Fables Wiki
Midnight wind is a clear substance, captured in clay pottery and held tight with a cork.
A special windscarf made of mystic hemp, with a dreamcatcher-like device utilizing special patterns at the mouth is necessary to capture midnight wind. Once one of these has been created, midnight wind can be created very rapidly by simply putting it outside in the wind, and putting the tail of the windscarf into a mundane clay jar. When one of these jars is filled, it will hum slightly, and the wind will only be banished if sunlight streams directly into the pot, giving a fairly long window of time to capture the substance. Ten jars of this can be gathered per age.
Midnight wind, when put into an alchemical mixture, creates a solution which will enhance the stealth of a creature, making them significantly more quiet. It can also mask the effects or presence of a specific ingredient, for a time.