Grease

Range: 30 feet
Area: 4 contiguous 5-foot squares
Duration: 1 minute

All solid ground in the area is covered with grease. Each creature standing on the greasy surface must succeed at a Reflex save or an Acrobatics check against your spell DC or fall prone. Creatures using an action to move onto the greasy surface during the spell's duration must attempt either a Reflex save or an Acrobatics check to Balance. A creature that Steps or Crawls doesn't have to attempt a check or save.