Dragon Classes (Franchise)

The dragons known by the Hairy Hooligan Tribe are grouped into one of seven classes based on their characteristics and abilities. The seven known classes are Stoker, Boulder, Fear, Sharp, Tidal, Mystery, and Strike. In the exclusive short, Book of Dragons, the idea to categorize dragons into individual classes was started by Gobber's great-great-great grandfather named Bork the Bold.

Stoker Class
Stoker Class dragons are hotheaded fire breathers, and most of them are capable of setting themselves on fire. They include the Terrible Terror, the Monstrous Nightmare, the Typhoomerang, and the Fireworm (whose queen can re-ignite other dragons' fires).

The only known dragons in the Stoker class is Hookfang,Torch and Sharpshot,Iggy,Butt and Head.

Boulder Class
Boulder Class dragons are tough and associated with the earth. They can eat rocks, and despite that their wings are smaller compared to their entire body, they are able to fly as fast and as high as most other dragons can. The Gronckle, Whispering Death, and the Screaming Death are members of this class.

The only known dragon in the Boulder class is Meatlug.

Fear Class
Fear Class dragons are stealthy, sneaky, and often have multiple heads. Instead of fire, they breathe gases with different effects. The known dragons of this class are the Hideous Zippleback and the Snaptrapper.It is possible that the Flightmare is in this class because its breath weapon consists of a paralyzing mist. Another Fear-class dragon is mentioned in How to Steal a Dragon's Sword, when Fishlegs asked Hiccup what he knew about the Brainpicker.

The only known dragons in the Fear class is Barf and Belch.

Sharp Class
Sharp Class dragons are vain and prideful, and they all possess sharp body parts. The Deadly Nadder, the Timberjack, and the Speed Stinger are grouped in this class.

The only known dragons in the Sharp class is Stormfly.

Tidal Class
Tidal Class dragons live in and near the ocean, and unlike most dragons, they don't have fire breaths as their ranged attacks. The Scauldron, the Thunder Drum, the Oceanzap, and the Bewilderbeast are classed here.

The only known dragons in the Tidal class is Thornado.

Mystery Class
Mystery Class dragons have little known about them. In this class are the Changewing, the Boneknapper, and the Smothering Smokebreath. Also, according to the How to Train your Dragon Live Spectacular's program book, the Red Death is a mystery class Dragon. Night Fury used to be Mystery Class, but thanks too Hiccup and Toothless, information on the Night Fury is now available.

Strike Class
Strike Class dragons are super fast, highly intelligent and have incredible vice-like jaw strength. They are also the most difficult to train, but the most loyal once trained. The dragons of this class are the Skrill and the Night Fury.

The only known dragons in the Strike class is Toothless.

Trivia

 * The Grapple Grounder is not grouped in any of the classes mentioned above, nor does it have one of its own. Though it's been described as being rather similar in behavior to a Night Fury, as well as having very similar firepower, it could be a Strike Class dragon.
 * Since the vikings didn't know what a Night Fury looked like until the taming of Toothless, the Strike Class should logically be symbolised by the Skrill. It is possible that the Strike class's symbol was changed by the Hooligans to have a new symbol after the taming of Toothless.
 * It is possible that the Mystery Class is a sort of "temporary" class where dragons are put when little is known about them, and then when they are more thoroughly understood they are moved to another class. For instance, the Night Fury could have been a Mystery Class dragon before the events of the first movie, and then moved to the Strike Class once it was studied and trained by Hiccup.
 * These seven classifications may not be the only ones in the future.