Bone Fists

Necromancy
Level: Artificer * 2, Bloodrager * 2, Cleric */Oracle * 2, Druid * 2, Hunter * 2, Shaman * 2, Sorcerer */Wizard * 2, Warlock * 2
Components: V, S, M (the knucklebone of a dire animal)
Casting Time: 1 Standard Action
Range: close (25 ft. + 5 ft./2 levels)
Target: 1 creature/level, no two of which can be more than 30 feet apart
Duration: 1 minute/level
Saving Throw: None (harmless)
Spell Resistance: no
  The bones of your targets' joints grow thick and sharp, protruding painfully through the skin at the knuckles, elbows, shoulders, spine, and knees. The targets each gain a +1 bonus to natural armor and a +2 bonus on damage rolls with natural weapons, and they are treated as having armor spikes, with which they are proficient.