This includes items and quests that can no longer be obtained or are now deprecated.
Arcane Concentration
Arcane Concentration(3 ranks)
Arcane, Tier 1
Gives you a 13/27/40% chance of entering a Clearcasting state after any damage spell hits a target. The Clearcasting state reduces the mana cost of your next damage spell by 100%.
Your next damage or healing spell or offensive ability has its mana, rage or energy cost reduced by 100%.
Duration: 15 seconds
Arcane Concentration is a Mage talent that gives you a chance to enter a Clearcasting state after any damage spell hits a target. The Clearcasting state lasts 10 seconds, and the next damage spell will cost no mana.
This talent is very popular with all types of mages, as it is nearly a 10% reduction in mana usage over time. Reduced mana use means a mage can focus his gear on other stats, such as spell damage, spell crit or stamina, depending on the situation. In practice, the Clearcasting state can proc just as an enemy dies, meaning the buff will expire before another spell is cast. This makes the talent most useful for longer fights, such as boss encounters, but it still improves efficiency in most all situations.
Tips and tactics[]
One technique is to use low cast time or high mana efficiency spells such as [Scorch] until a Clearcasting procs. Then use a higher damage spell that has lower efficiency, when the casting cost is free. In instances or solo'ing, you can also cast Scorch until Clearcasting procs, then fire off a [Blizzard]. Combined with [Arcane Potency], which at max rank gives a +15% crit chance when Clearcasting or Presence of Mind activates, this can be a lethal attack.
Hotfix (2010-11-23):Arcane Concentration will not go on internal cooldown when it fails to proc.
Patch 4.0.3a (2010-11-23): Now has a much higher chance (13/27/40%) of entering a Clearcasting state. This effect cannot occur more than once every 15 seconds. The tooltip still states that there is a 3/6/10% chance, as it averages out to approximately the same chance with the internal cooldown applied.
Patch 4.0.1 (2010-10-12): It's now a Tier 1 and 3 Ranks talent, down from Tier 2 and 5 Ranks. Now has a 3/6/10% chance to proc, up from 2/4/6/8/10%.
Patch 3.3.0 (2009-12-08): The interaction of this talent with [Arcane Missiles] has been restructured. Instead of an Arcane Missiles cast triggering the talent, each missile has an independent (but reduced) chance to trigger this talent. In addition, the talent will no longer sometimes be triggered from misses by Arcane Missiles, [Arcane Blast] and [Blizzard].
[Scorch] until a Clearcasting procs. Then use a higher damage spell that has lower efficiency, when the casting cost is free. In instances or solo'ing, you can also cast Scorch until Clearcasting procs, then fire off a 
[Blizzard]. Combined with 
[Arcane Potency], which at max rank gives a +15% crit chance when Clearcasting or Presence of Mind activates, this can be a lethal attack.
Patch 5.0.4 (2012-08-28): Removed. 
