Blizzard

Crystalline spears of ice plummet to the ground at four different points you can see within range. Each creature in a 40-foot-radius sphere centered on each point you choose must make a Dexterity saving throw. The sphere spreads around corners. A creature takes 20d8 cold damage on a failed save, or half as much damage on a successful one. A creature in the area of more than one Blizzard burst is affected only once.

The ground afterwards becomes covered in ice for 3 rounds and is considerd to be difficult terrain. And when a creature moves while on the ice, it needs to make a Dexterity DC: 10 saving throw or become prone.