Eruption of Force

You raise your hand above your head, palm upwards. Above your palm, a 2-inch ball of blinding magical force coalesces. At this point, everyone in a 20-foot radius of you(including you) must make a DC 15 Con save or become blinded for as long as you maintain concentration. Then, provided you are not blinded, a lot of darts  made of magical force, similar to those in the magic missile spell erupt from the orb. Any number of creatures you choose within one mile are hit by darts. The darts strike simultaneously, and each creature can only be targeted by one dart. A creature which is immune to the magic missile spell is immune to this spell. A creature hit by the dart takes 6d6 force damage for a 7th level spell slot, 7d6 for an 8th, and 8d6 for a 9th.