Abyssal Wave

 You unleash a wave of dark water in a 15-foot cone. Each creature in a 15-foot Cone makes a Dexterity saving throw, A creature takes 3d6 necrotic and lighting damage on a failed save, or half as much damage on a successful one. Additionally, each creature that fails the save is pushed 10 feet away from you.

Using a Higher-Level Spell Slot. The damage increases by 1d6 for each spell slot level above 1.