Blizzaga

You unleash the full, frigid majesty of the Water Crystal, causing the atmosphere to collapse into a massive column of permafrost. Creatures of your choice in a 30-foot-radius, 60-foot-high Cylinder within range must make a Constitution saving throw. taking 8d8 Cold damage and gaining the [condition]Restrained[/condition] condition until the start of your next turn. On a successful save, it takes half as much damage and is not Restrained.

Whether a creature saves or not, the ground within the cylinder's footprint is instantly flash-frozen, becoming Difficult Terrain for 1 minute.