As an action, you can create this vial of light blue liquid. As an action, a creature can throw the vial at a point within 9 meters. A thin layer of ice covers the ground in a sphere that is twice as big as normal centered on the point and turns it into difficult terrain for the duration.
When the ice appears, each creature standing in its area must succeed on a Reflex saving throw or fall prone. A creature that enters the area or ends its turn there must also succeed on a Reflex saving throw or fall prone.