Blade Storm

As you cast this spell, choose a point you can see within range. A 100 foot-radius black portal appears above the ground, forming a 500 foot tall cylinder. Creatures who start their turn in this area, or enter the area for the first time on a turn, must make a Dexterity saving throw or take 6d6 piercing damage as a hail of blades rains from the sky. On a successful save they take half as much damage.

As an action while maintaining concentration on this spell, you can choose one creature within the area of effect. You send a thick band of raining swords at them, forcing another Dexterity saving throw, resulting in 10d10 piercing damage on a failure, or half as much on a save. 

After the termination of the spell, all conjured blades disappear.