Black Ice

A slick of cold magic flows across the ground, coating the terrain in thin, almost invisible ice. A 5ft by 5ft area of solid terrain becomes difficult terrain for the duration of the spell. 

Creatures that move into this area for the first time make a perception saving throw to notice the ice. on a failed save, they are knocked prone, and suffer 1d6 bludgeoning damage.

casting this spell at higher levels increases the area by 5ft per spell level above 0.