As a reaction, you can attempt to freeze a creature that missed a melee attack against you. The creature that triggered this reaction makes a CON save against your spell save dc. A creature takes 8d4 cold damage on a failed save and becomes restrained in ice, or half as much damage on a successful one and isn't entombed. 

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the damage increases by 1d4 for each slot level above 3rd.