Barkskin

Player's Handbook v.3.5 (PH)Core (3.5)
School
Transmutation
Casting Time
1 standard action
Components
V, S, DF
Range
Touch
Target
One living creature
Duration
10 minutes/level
Saving Throw
None
Spell Resistance
Yes (harmless)

Barkskin toughens a creature’s skin. The effect grants a +2 enhancement bonus to the creature’s existing natural armor bonus. This enhancement bonus increases by 1 for every three caster levels above 3rd, to a maximum of +5 at caster level 12th.

The enhancement bonus provided by barkskin stacks with the target’s natural armor bonus, but not with other enhancement bonuses to natural armor. A creature without natural armor has an effective natural armor bonus of +0, much as a character wearing only normal clothing has an armor bonus of +0.