You are made of cracked stone. While you remain motionless, you are indistinguishable from a normal statue. You gain a +1 natural bonus to your Armor Class, and also gain immunity to the petrified condition, and you do not suffer the negative effects of exhaustion (unless it was induced by a lack of long rest) until the sixth stage.
Unfortunately, you gain vulnerability to bludgeoning damage, and you have disadvantage on stealth checks while moving.