You sap all heat from your surroundings within 20 feet, creating an aura devoid of warmth. Once per turn, creatures who enter or end their turn within the area must succeed on a Constitution saving throw or take 10d8 cold damage. Creatures who succeed take half damage.

All creatures within the area other than yourself have their speed reduced by half while in the area. 

Any creature that spends two full turns in the area must succeed on a Strength saving throw or be stunned for 1 round as they are frozen in place.

Additionally, any water within the area is instantly frozen. Any creatures in the water are frozen in place, reducing their speed to zero, and must make a Strength saving throw against your spell DC to break free. If any creatures are at least waist deep in water when it is frozen, they are considered petrified until broken free by another source or the ice melts.