Crackle Bag

This inconspicuous bag creates a number of small inconspicuous items with a peculiar property – they emit a loud cracking sound if squeezed or thrownagainst a hard surface.
Benefit: You may use this magic bag to create several small innocuous bits of wood, stone, or metal that cover a number of squares dependent on the action used to place them. Five times per [Scene], as a swift or as part of a move action, you may coat a 15 ft square within [Close] range. Five times per [Scene], as a standard action, you may coat a 30 ft square within [Close] range. Items created by the Crackle Bag last until the end of the current [Scene]. You may make a Larceny check as with Traps to conceal the nature of the items when deploying them. Whenever these items are placed onto a square occupied by a creature, or whenever a creature moves into a square occupied by these items, the items crackle and leap at the intruder.

Any creature within your [Close] range of the crackling items automatically knows from which square the items crackled and leaped. Any creature within your [Medium] range of those items knows the general direction of those items. If a creature is aware of the items, they may opt to treat intentional movement through the squares occupied as difficult terrain to avoid making the items crackle.