Vel'n's Razors

The Drow Wizard Vel'n Lothroth harnessed the air itself in to a razor thin blade.

You summon a transparent blade of wind that cuts through your enemies. Each creature in a 60ft long, 5ft square, in front of you makes a Dexterity saving throw. Each creature takes 2d6 slashing damage on a failed save and none on a successful save. 

At level 5 you can summon 2 Blades of Wind and send them in different directions.

At level 8 you can summon a Third blade of Wind

Each Blade does the same damage.  You cannot send more than one blade down the same path.

At Higher Levels. When you cast this spell using a spell slot of 2nd level or higher, the damage increases by 1d6 for each slot level above 1st.