The Breathquencher resembles a gigantic python in both appearance and function. They grow to be in excess of twenty feet long and are depicted as having rainbow coloration with red eyes and being quite nice-looking. They have sharp teeth sticking out of their upper jaw, and have spikes from head to tail, ending in a Stinger-like tail. There are two horns on their head, and a pair of large wings. As with snakes, Breathquenchers do not have legs but slither along the ground and up trees.
Breathquenchers are classified as a Tree Dragon in The Incomplete Book of Dragons, however, Hiccup indicates in How to Steal a Dragon's Sword that they dwell in caves, suggesting they are Cave Dragons.
Breathquenchers are stealthy and catch their prey with their muscular coils, squeezing them to death as most constrictor snakes do. Breathquenchers, like snakes, can also unhinge their jaws in order to consume large prey, such as a Giant Bee-Eater.
Breathquenchers are described as being intelligent, but vain.
The Incomplete Book of Dragons also indicates that Breathquenchers have superb eyesight, X-ray vision, and a good sense of smell. They are also listed as being chameleons, but it is not clear if they can actually change colors or just have good camouflage.
Despite the Breathquencher's intelligence, they can be side-tracked by showing them a mirror in which to look at their own reflection.
Breathquenchers rate a "6" in disobedience, indicating they aren't impossible to train, just difficult.
Breathquenchers joined with Furious' dragons in the Dragon Rebellion.
The Purple Death uses a fighting technique called the "Breathquencher hug" to grip on tightly to the Green Death when they begin to fight eachother.
This reference book details the Breathquencher and provides and image. Breathquenchers are also listed in a statistics table in the back of the book.