Any piercing attack from the flank or rear has a 10% chance of popping the inflated anal gland of the stank hog, releasing the noxious flatulence and causing the full effect as described under the mephitic gas action. Additionally, any piercing or slashing critical hit from the flank or rear has a 50% chance of popping the inflated anal gland and triggering the mephitic gas action, the mighty blow cutting deep into the stank hog's thick hide and puncturing the gas-filled gland. If stank's revenge is activated, the hog can no longer use the mephitic gas attack until it is able to heal for one week.