Your Arcane Blast has a 100% chance and your Fireball, Pyroblast, Frostfire Bolt, and Frostbolt spells have a 50% chance to grant Stolen Time, increasing your haste rating by 50 for 30 sec and stacking up to 10 times. When Arcane Power, Combustion, or Icy Veins expires, all stacks of Stolen Time are lost.
