Powder

A bag of powder contains powdered chalk, flour, or similar materials. In addition to other uses for powder, it can be handy while adventuring to help pinpoint invisible creatures. You can throw the powder into an adjacent square as an action. If there's a creature in that square, it becomes temporarily until the end of your turn, though the creature still has Concealment due to invisibility. The powder quickly falls away or becomes invisible itself, preventing you from tracking the creature indefinitely.