Crystal Dust

You point at a location within range, and a 1-foot-diameter snowflake of cold energy appears there and explodes in a 20-foot-radius sphere. Each creature in that area must make a Constitution saving throw. On a failed save, a creature takes 3d8 cold damage, and is covered with crystal dust until the end of your next turn. On a successful save, a creature takes half damage and isn't covered with crystal dust.

The first time a creature covered with crystal dust is hit by a melee weapon attack it takes 7d8 bonus cold damage as the crystal dust shatters away.

At Higher Levels. When you cast this spell using a spell slot of 5nd level or higher, the melee weapon attack bonus damage increases by 1d8 for each slot level above 4th.