Steadfast Gut-Stone

This fist sized chunk of off-white stone seems too large to fit inside a human's mouth, but may be swallowed with ease as a standard action. Once ingested, the gut-stone remains active for up to a week, maneuvering itself within the body to protect its bearer's vital organs. Any time an attack would subject the bearer to precision-based damage (such as a critical hit or sneak attack), that damage is instead directed to the gut-stone. All other damage from the triggering attack, as well as damage that surpasses the gut-stone's hit points, is applied to the character normally. A gut-stone has 10 hit points and hardness 0.

When a gut-stone is damaged by a melee weapon attack, as a free action its owner may sacrifice the stone to damage the attacker's weapon. Treat this as the bearer making a free sunder combat maneuver against the weapon, except that it does not provoke an attack of opportunity, bypasses the weapon's hardness, and deals 1d4 points of damage.

Only one gut-stone may be in a creature's body at a time. Any attempt to swallow a second destroys both stones and forces the creature to make a DC 15 Fortitude save or be sickened for 1 round. If a gut-stone is not used within a week of being swallowed or is destroyed it crumbles apart and is passed harmlessly out of the body.