Death from Below

Twin spectral blades flash into existence from you to a point you choose within range and you can see. The blades 10 feet high and each is 25 feet long creating either an X or + shape chosen by the caster. Each creature in the area must make a Dexterity saving throw, taking 5d6 Slashing damage on a failed save or half as much damage on a successful one.

 For each creature slain any creature effected by the spell takes an additional 1D6 slashing damage. Creatures who previously succeeded on the Dexterity saving throw continue to take half damage from this effect. This effect continues until no additional creatures are slain by this effect on this turn.

 If using a tiled grid:

• X Shape: The blades form a diagonal cross, extending 2 spaces in the diagonal directions from origin space.  The total reach from one tip to the opposite is 25 feet.
• + Shape: The blades form a horizontal and vertical cross extending 2 spaces in the horizontal and vertical directions from origin space.  The total reach from one tip to the opposite is 25 feet.

Using a Higher-Level Spell Slot. The damage increases by 1d6 for each spell slot level above 3.

 Inspired by spell by the same name in League of Legends.