Mirror Image

Mirror Image is a Mage spell of the Arcane tree. Casting it creates three copies of the Mage around him that cast spells at his current target and have a fraction of his health and intellect. This ability was added in Wrath of the Lich King and is trainable at level 50.

Details
This spell was previously not affected by the global cooldown nor triggered it. However, since Patch 3.1.0 this spell is on the global cooldown. However, it does not trigger a GCD on every other Mage spell that doesn't have a global cooldown such as Cold Snap, Icy Veins, Combustion and damage trinkets.

The images created do low damage and receive a percentage of the Mage's intellect. Without Glyph of Mirror Image, they cast 3.0 second Frostbolts and occasionally shoot Fire Blasts. With the Glyph, they cast Arcane Blast or Fireball depending on spec. Mirror Images inherit the spell hit chance of their master's gear, but not haste or crit. Arcane Power or Mana Adept further increases their damage as well as their master's Arcane Blast stacks.

Mirror Images inherit 33.33% of their master's spell power each. their Frostbolts do 163-169 + 30% of that spell power as frost damage and crit for 200% of their normal damage (aside from snaring their target by 40% for 4 secs), while the Fireblasts do 88-98 + 15% of that spell power as fire damage and crit for 150%.

Tips and tactics
The Mirror Images inherit the Mage's threat lists, and the Mage also gains a 90M threat reduction debuff like Fade. This makes it useful as a last-ditch threat dump. The images do an average of 15k damage over 30 seconds with no spell power, which is highly useful for single-target DPS in raids and sustained PvP burst.

Known bugs

 * Mirror Images often do not attack the highest threat target when summoned and may also attack mobs not engaged in combat, but within range.
 * As of 4.0.3, when a mob is attacking the mage and the images are summoned, the mob may still continue to attack the mage sometimes.
 * In certain locations, like the room of the third boss in the Stonecore, summoning the images pulls all mobs in the room on the party.