You cast a bluish and minuscule energy ball from your hand at a point you choose within range that explodes in  a sphere of blue cold flames. Each creature in a 20-foot-radius sphere centered on that point must make a Dexterity saving throw. A target takes 8d6 frost/fire damage on a failed save and becomes frozen during 3 turn, or half as much damage on a sucessful one and not frozen.

Aditionally the area becomes covered by ice and becomes difficult terrain for 3 turns. Any creature that walks over the area more than 5ft must make a Dex saving throw or fall phrone, unless it has some mean to avoid sliping on the ice. If the surface is in a slope, the creature will slide through that slope.

Frozen effect: A creature inmune to Ice damage can break from the ice as a move action, otherwhise a Frozen creature can make a Strength saving throw at the end of its turn to break the ice earlier.  Appart from that, being Frozen is like being Paralyzed.

At Higher Levels. When you cast this spell using a spell slot of 5th level or higher, the radius of the sphere will increase in 5 ft per additional level beyond 4.