Exhaust of the dragon
Most folk who are not familiar with the skill "Exhaust of the dragon" assume that a practitioner would breathe fire out of their mouths. Those that have learned the skill know just how wrong that is. But in order to avoid embarrassment when using the skill, you will often see the person bend over slightly and open their mouths. What actually happens is known in semi-polite society as a "fart". The exhaust of a dragon is a fragrant collection of smells intended to lie an opponent low.
Level 1-5 Those first learning this skill start with a slightly modified diet. Consisting mostly of nuts and tree bark (usually without salt since the gods seem to be a little stingy when it comes to spices.) This highly fibrous diet helps the hero develop and trap the necessary gasses to practice this skill.
Level 6-10 As the hero becomes accustomed to the new diet, other more exotic vegetable matter is added to meals. Most heroes are eager to start adding more variety to their diet. That is until they find out how much chewing is involved.
Level 11-15 A hero who reaches this level of skill has a digestive track able to handle just about anything. And just about anything is what they eat. The more varied and exotic the diet, the more varied and exotic the "exhaust."
Level 16-20 At this point a hero rejoices in their mastery of this skill. They have finally figured out how to use the bubbles in the beer they drink to power up the gases mixing away in their intestines. When a hero of this level lets out the "exhaust" EVERYONE knows it.