Mage Armor
From HGWiki
Caster Level(s): Bard 1, Wizard / Sorcerer 1
Innate Level: 1
School: Conjuration
Descriptor(s): Force
Component(s): Verbal, Somatic
Range: Touch
Area of Effect / Target: Single
Duration: 1 Hour / Level
Additional Counter Spells:
Save: Harmless
Spell Resistance: No
Description: The selected target gains +1 Dodge, Deflection, Natural, and Armor AC. The dodge bonus stacks with other dodge bonuses to AC, but the other bonuses do not stack with bonuses of the same type. At caster level 21, the AC bonuses are doubled to +2 of each type, and at caster level 41, the AC bonuses are increased to +3 of each type. With spell focus feats in Abjuration, the Armor AC bonus increases to 4 AC per feat when the caster targets himself, topping out at +28 (yes you are reading that correctly!) if you specialise in Abjuration.
Notes
As a character acquires enchanted equipment, the effectiveness of this spell goes down, due to the non-stacking bonuses. At higher levels, typically only the dodge bonus has an effect, and even that is wasted if the +20 dodge bonus cap has been reached. Earlier mage armors (but not shadow variants) are removed from the target when this is cast.