Corrupting Chill

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 black crystals grow from the wound left behind. The creature must make a Constitution saving throw against your spell save DC, and on a failure has a -1 penalty to attack rolls until the start of your next turn. Additionally, the affected creature takes cold damage equal to your spellcasting ability modifier at the start of its next turn or half as much if it succeeded on its saving throw.

At Higher Levels. At 5th level, the melee attack deals an extra 1d6 cold damage to the target on a hit, and the damage the target takes for moving increases to 1d6 + your spellcasting modifier. Both damage rolls increase by 1d6 at 11th level (2d6 and 2d6) and again at 17th level (3d6 and 3d6). Starting at 11th level, the penalty to attack rolls the target suffers is now -2.