The Piranha Hermit Dragon has quite a particular name. Despite that, this dragon is mentioned only once in How to Seize a Dragon's Jewel, as one of the many odd dragons found in the Amber Slavelands. "He was so scared he could hardly think. How could he be attacked from inside the castle? What could this be? His mind jostled with Rocket-Rages, with Piranha Hermit dragons, with something worse than all of these . . ." ―Hiccup after being abducted within Prison Darkheart