You create a shallow extra-dimensional hole perfectly sized to trip anyone who steps within it. This hole occupies a single 5-foot square with a depth of six inches. Any creature occupying the square when you first create the hole, or who later steps into the square containing the hole, must make a Reflex saving throw to avoid falling prone in an adjacent square and taking 1d6 points of damage. A creature that makes its saving throw still stumbles ever so slightly and takes a -1 penalty on all rolls and checks for 1 round. The spell has no effect on creatures adjacent to the square containing the hole.