|“||No, he would send Tongue-twisters, Gorebreathers, Brainpickers—all the most fearsome dragons in this dragon army||”|
|— Furious' strategies|
|“||She would send out a party of their most fearsome and pitiless dragons to destroy Hiccup before he got to Tomorrow: Hellsteethers, Tongue-twisters, Gorebreathers . . . just in case.||”|
|— Luna's plans|
The Gorebreather is a dragon mentioned three times in How to Fight a Dragon's Fury.
There is no physical description or image of a Gorebreather.
|“||Gorebreathers, Tongue-twisters, Hellsteethers, his brain told him helpful. Armed with poisonous gases, arm-twisting tongues, jaws that leapt out and get you . . .||”|
|— How to Fight a Dragon's Fury|
This passage tells us that Gorebreathers breathe toxic gas (Tongue-twisters twist limbs with their tongues and Hellsteethers have extendable jaws). No other description of abilities or appearance is given.
Though no Disobedience score is given, the Gorebreathers are portrayed as violent and fight for Furious against humans in the Dragon Rebellion. This said, Gorebreathers are probably not very trainable, if at all.
Gorebreathers are mentioned in this final Book as a species that sided against humans.