A flurry of magic snowballs erupts from a point you choose within range. Each creature in a 5-foot-radius sphere centered on that point must make a Dexterity saving throw. A creature takes 3d6 cold damage and its speed is reduced by 10 feet until the start of your next turn on a failed save, or half as much damage and no movement speed penalty on a successful one.   The area of effect is then considered difficult terrain for one minute.