Description
This is one of the oldest and best known dragons in the franchise, having roots that stretch all the way back to the original book series. This Monstrous Nightmare is in some ways a foil to the books version... the book version is described as getting no bigger than a small riding dragon when fully grown, and it has four legs, and rather devilish styling, with a pair of intimidatingly curved horns and a barbed tail spade. They're also described as mainly coming in three colors: Scarlet, Purple, and Green. Only one Monstrous Nightmare, which is stated as belonging to the son of the Meathead Chief in the first book, is stated to be another color, that being silver.
Fun Fact: The Monstrous Nightmare had a tentative wyvern design even when HTTYD was going to follow the plot of the books. This is evidenced by early storyboards in which Snotlouts Monstrous Nightmare (then presumably still named Fireworm) is drawn as a wyvern. These storyboards depict a scene where Snotlout, his lackeys, and their hunting dragons bully Hiccup, Fishlegs, and their hunting dragons... and Toothless eventually throws an insult of his own at Snotlouts hunting dragon, who's so shocked they briefly spit fire as they're being... erm... walked along by Snotlout.