Mage Armor is a passive level 56 Arcanemage ability that increases the mage's Mastery, and reduces the duration of all harmful Magic effects used against the mage by 25%. Mastery is increased by 3000 at level 90.
Patch 6.0.2(2014-10-14): Now a passive effect and is available only to Arcane mages.
Patch 5.1.0(2012-11-27): Now reduces the duration of harmful Magic effects by 25%, down from 35%.
Patch 5.0.4(2012-08-28): Redesigned. Mage Armor now increases Mastery, and no longer regenerates mana or increases Resistances. This spell is now available at level 80, up from 68. In addition, a 3-second cast time has been added, there is no longer a duration, and it now persists through death.