Presence of Mind is a mage talent available at level 15. When activated, it causes the next spell with a casting time less than 10 sec to be instant. For example, activating Presence of Mind and then casting Pyroblast will instantly hurl a fiery ball without that spell's normal 6 second casting time. Presence of Mind only affects spells with a cast time less than 10 seconds, which only excludes Teleport and Portal spells.
After activating Presence of Mind, a buff appears indicating the next cast will be instant. This buff will remain indefinitely until the effect is used. The cooldown will not begin until this current buff is consumed.
With enough haste, a mage should reduce the cast time for Teleport and Portal to work with the spell. However, trying to cast those spells while under Presence of Mind will normally cast them, whithout consuming the buff.
Presence of Mind is used mainly to achieve burst damage. It is often used in conjunction with Arcane Blast, Frostfire Bolt, or Pyroblast to deal a large amount of damage without the normal cast time.
Once Presence of Mind is activated, the next instant spell can be cast while on the move, where it would normally require the mage to stop and cast. Thus, it can be used to cast large nukes while jumping or falling.
This ability is also useful with Polymorph. Sometimes a mob is beating on you and casting Polymorph will take longer due to damage interrupts, or the mob is a hard-hitting elite and will one-shot you, and an instant Polymorph is needed to survive.
This ability is popular with the so-called Three-Minute Mage, a play style that gets its name from this ability and Arcane Power, which both originally had a 3-minute cooldown.
Patch 4.0.6 (8-Feb-2011): When Presence of Mind was active, Conjure Mana Gem was not becoming an instant cast spell if used to refresh a stack of 2 or less Mana Gems. This has been fixed.; Presence of Mind is no longer consumed when Flame Orb is cast.
Patch 3.0.9 (2009-02-10): Arcane Power and Presence of Mind now share a category cooldown. Arcane Power causes a 15 second cooldown. Presence of Mind, once consumed, causes a 1.5 second cooldown.
Patch 3.0.9 (2009-02-10): Presence of Mind: The cooldown has been reduced to 2 minutes, (down from 3.)