Glacies Via

At-will, standard action, concentration, DC 15+; you freeze a surface within 60 feet, creating a sheet of ice covering up to a 30-foot square. The area becomes difficult terrain. A creature entering the area or starting its turn there must make a Dexterity save or fall prone. The ice is slick enough to slide on—you can choose to skate across it at double speed with a DC 13 Acrobatics check.

• DC +2: the area doubles (stackable).
• DC +4: you can create the ice vertically (on walls) or overhead (on ceilings). Climbing creatures must make Dex saves or fall.
• If created on water, the ice is thick enough to support the weight of a horse and rider.