(2) Set: You have a chance to summon a Mirror Image to assist you in battle for 15 seconds when you cast Frostbolt, Fireball, Frostfire Bolt, or Arcane Blast.
(4) Set: Your spells have an increased chance to trigger Brain Freeze or Hot Streak. In addition, Arcane Power decreases the cost of your damaging spells by 10% instead of increasing their cost.