Origin of the breath weaponEdit
All breath weapons seemed to evolve around a certain time period. Historians believe that at one point when the population of dragons was at its peak, every dragon began to develop their own, unique breath weapon in order to defend themselves from enemies. They are not sure of the exact date and there are plenty of estimates.
How it is producedEdit
Humans have speculated how dragons produce their breath weapons for centuries. Even today, we still know little about it, but we may have a few ideas.
Breath weapons stem either through magic or from a "Draconis Fundamentum," located either in the dragon's throat or chest. The Fundamentum contains and produces key ingredients for fire breath. As fire is the only type that has a fully plausable theory, I will explain that here.
Fire breathing Dragons have 2 stomachs. One is for digesting food in the digestion system. However, the second stomach is part of the "Incendius" system. Here, the food is broken down further into natural gases, such as methane. This is then stored in the bottom half of the Fundamentum, as oxidising agents are produced into the top.
What now? Well, the Fundamentum is lined with muscle, giving the dragon full control. If s/he wants to breathe fire, they contract the muscles, forcing the oxidising agent and the fuel into the throat. As the agent hits oxygen, it combusts, igniting the fuel. Now, the Dragon simply blows hard to produce a constant flame.