Demonflesh

The caster grows the thick, leathery flesh of a demon

Book of Vile Darkness 3.5
By Monte Cook

Transmutation [Evil]

Level: Blackguard 1, Demonic 1
Components: V, S
Casting Time: 1 action
Range: Personal
Target: Caster
Duration: 1 minute/level

Gaining a +1 natural armor bonus to Armor Class for every five caster levels (at least +1, maximum +4). This spell has no effect if the caster is an evil outsider.