While making an attack, the stank hog lets forth a vile gust of air accumulated in its specialized anal gland. Roll 1d20. On a result of less than 10, the anal gland deflates and adheres to itself, rendering the mephitic gas for that stank hog unusable until it completes a long or short rest. A result of 10 or higher creates a 10-foot-diameter gas cloud; 15 or higher creates a 20-foot-diameter gas cloud; and a roll of 20 creates a 30-foot-diameter gas cloud. The effect is immediate and profound, affecting all creatures within the cloud. Any creature that starts its turn within the gaseous cloud or enters the cloud on its turn must make a successful Constitution saving throw, the save DC equaling the stank hog's roll, or become incapacitated. While incapacitated from the mephitic gas, the creature lies upon the ground with eyes stinging and vomit flowing. An incapacitated creature may make another saving throw at the start of its turn, ending the effect upon itself on a success. The mephitic gas lasts for 1d4 + 1 rounds, lingering in the same area unless a strong wind disperses it. The stank hog is immune to its own and other stank hogs' mephitic gas.