"There are Riproarers - horrible creatures that dribble and scream."

Riproarers are muscular cave dwellers that were one of the first dragons to join the Dragon Rebellion in How to Steal a Dragon's Sword. A Riproarer tears its victims to pieces, but might let you alone if you have recently eaten parsnips, as they find this root vegetable repugnant.

A group of Riproarers is referred to as a Swarm.

Traits and Abilities

Riproarers can squeeze themselves into spaces as small as a human hand, due to a collapsible skeleton. Even their skulls can flatten, with sections sliding over one another. They share this ability with one other related dragon - the Raptortongue.

"Black frothing slobber foaming at the mouth; red-veined eyes quivering; its hot, indescribably stinking and repellant breath scalding Hiccup's cheeks."
How to Steal a Dragon's Sword

There is some variation with their coloration. In How to Steal a Dragon's Sword they are described as greenish, but in The Complete Book of Dragons: A Guide To Dragon Species, they are depicted as purplish. They also have acidic blood.