Magic Salt is a white powder that is used to form a barrier of protection against danger, especially during Midsummer's Eve . When placed in a thick line on the floor, a Goblin, for instance, will not cross it. When scattered in the air, it produces a twinkling cloud of dust particles filled with energy that repels any would-be attacker.  In the first book of Fablehaven, Stan Sorenson sprinkles the Magic Salt around Kendra and Seth's beds in order to protect them on the night of Midsummer's Eve. Magic Salt is not as effective as Flash Powder, but safer to use. 

Source

• Fablehaven (Fablehaven #1)
• The Caretaker's Guide to Fablehaven