Volt Surge

You conjure a surge of pure electrical energy and blast it at one creature within range.  The target must make a Dexterity saving throw.  On a failed save, the creature takes 10d6 lightning damage and it falls prone.  In addition, if the target is hit by an attack before the end of your next turn, the attack deals an additional 3d6 lightning damage.  On a successful save, the creature takes half damage, falls prone, but does not take additional damage from other attacks.

At Higher Levels.  When cast using a spell slot of 6th-level or higher, this spell deals an additional 2d6 lightning damage per spell slot level above 5th.