The Fire Fury is a Mythical Dragon that exists in Berk's mythology. It is unconfirmed if they exist, and it is very unlikely that they do, however, every so often a sighting is reported. It is likely that these sightings are just of Toothless, an Ice Fury, or a Light Fury. These dragons are obviously not in the Book of Dragons. If they do happen to exist, it is likely that they would fall into the Stoker Class.
Want to learn more about Fury Dragons? Check out these pages!