Boreal Blade

You brandish the weapon used in the spell’s casting and make a melee attack with it against one creature within 5 feet of you. On a hit, the target suffers the weapon attack’s normal effects, and must make a constitution saving throw. On a failure, the target takes 1d6 cold damage and cannot take reactions until the beginning of your next turn. The spell ends at the start of your next turn or if the target takes fire damage.

At Higher Levels. At 5th Level, the melee attack deals an extra 1d6 cold damage and the damage for a failed save increases to 2d6. Both damage rolls increase by a 1d6 at 11th level (2d6 and 3d6) and the target has disadvantage on the save. At 17th level the damage die increases by 1d6 (3d6 and 4d6) and the target speed is reduced to 0.