Stone Form

 
Prerequisite(s): Con 13+, Wild Shape
 
Benefit: As a standard action, you can spend one of your uses of wild shape to assume a stony and rocklike form. While in this form, you gain a +4 bonus on Fortitude saves against poison. Your natural armor bonus becomes +4 (replacing any natural armor bonus you normally have, though you retain any enhancement bonus to natural armor). You also gain a slam attack that deals bludgeoning damage equal to a morningstar appropriate to your size (2d6 points for Large characters, ids points for Medium characters, 1d6 points for Small characters).
 
Source: Races of Stone