Dragon breath

Dragon breath, or breath weapon, was a term used to refer to a special ability that was inherent to dragons and the majority of dragonkind, even those who merely had draconic ancestry. Depending on the type of dragonkind or draconic ancestry, this breath had different properties, with there being nearly as many varieties of dragon breath as there were types of dragons.

Magic
The dragon breath had an inherently magical nature. Some believed that the magic permeating the Prime Material plane empowered it. Others believed that the different species of chromatics, as well as metallics, were each imbued with elemental magic and their breath weapon was a manifestation of that elemental energy.

Sometimes, a dragon's breath could be affected by the magic that permeated within their lairs. Such as clinging to and lingering on those afflicted by it or recharging at an incredible rate.

With sufficient practice, some dragons were capable of shaping their breath weapon into a bipedal, elemental creature known as an animated breath.

History
On Toril, some scholars from Candlekeep proposed the proto-dragon theory, claiming that the dragons of their world gradually developed breath weapons through evolution. This theory purported that a common ancestor, ignidraco, developed a digestive tract that allowed them to regurgitate their own intestinal gas and ignite it with an enzymatic, hypergolic reaction in the back of their throats. The proto-dragon theory went on to claim that the ancestors of green dragons and black dragons developed their breath weapons from further modifying their digestive tracts.

There were many detractors to the proto-dragon theory, who pointed out that it could not fully explain the myraid of other elemental and non-elemental breath weapons that dragons possessed.

True Dragons

 * Almost every kind of dragon, including wyrms and faerie dragons had this innate power and ability.
 * There were a number of chromatic and metallic species of dragons that had similar types of dragon breath.
 * Crossbreed dragons, those born through the mating of two different species, could potentially develop a breathe weapon that was a combination of both their parents'.

Dragonkind

 * Most dragonborn were capable of exuding some type of dragon breath. The type of breath weapon was dependent upon what chromatic, metallic, or gem draconic ancestry the dragonborn had. And some believed that, like dragons, dragonborn were imbued with elemental magic. Some dragonborn whom believed this would claim that the dragon deity Io had gifted them that power as a sign of his favor. Regardless of its origin, it was typically as powerful as that of a wyrmling of the same type.

Magic

 * Rarely, weapons could be magically altered or enchanted to produce dragon breath.

Undead

 * Dragons resurrected as lesser forms of undead dragons lost their breath weapons, such as skeletons and zombies, though some sources claimed that zombies retained a weaker version of their breath weapon.
 * Dracolichs retained the breath they had in life, but were required to eat in order to refuel it.
 * The ghosts of dragons had their own unique form of breath that was a cone of gray mist, which sometimes took the form of a ghostly parody of the breath they had in life.
 * Hoarder dragons retained the type of breath they had while alive, but with an added spray of pelting coins