A small ball of blue and white energy leaves the tip of your finger and flies to a point you can see within range, exploding upon impact with a sharp crack and covering surfaces in a 20 foot radius sphere centred on that point with snow and frost. Each creature in that area must make a Constitution saving throw. A target takes 5d8 cold damage on a failed save, or half as much damage on a successful one. Until the end of your next turn, a creature that enters the area for the first time on a turn or starts its turn there must succeed on a Dexterity saving throw or slip on the ice coating and fall prone.