Call of the Storm

You call forth a storm of immense power and hatred. Bringing forth the storms hellish powers. Each round a up to 3 creatures of your choice must make a Dexterity saving throw or be hit by a bolt of lightning that deals (10d12) lightning damage of a fail, and half as much on a success. If another caster uses the spell call lightning each hit from one of the call lightnings' bolts deals an extra (2d8) lightning damage.