Aeldredd's Mystical Halo

When you gesture wildly with your finger, a whirling halo of magic missiles appears around your head.  On the turn you cast it, and as a bonus action on following turns, you may fire them at enemies or use them to deflect attacks. 

The number of missiles that appears is N = 2x[level cast at] + INT modifier.  Thus, a wizard with INT 16 (+3) who casts it at 4th level gets 11 missiles. 

You may fire volleys of up to [level] missiles per round until they are exhausted. 

Also, when hit by an attack, you may use your reaction to spend up to [level] missiles to reduce the damage done.  Each missile spent in this manner reduces damage done by 5HP.

Any missiles still active when the spell ends target the caster, who may not divert this damage in any fashion.

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Note:  this spell is modeled in part on Melf's Minute Meteors, a 3rd level spell with the same 10-min duration that throws 6x2d6 meteors (with 5' burst radius), up to 2/turn, which does NOT require concentration.  Thus, I don't think it's OP.