How to Train Your Dragon Wiki
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Why didn't you get one of those new Monstrous Nightmares with the six-foot wing-span and the extra-extendable claws? They're really mean killers, they are.
  Speedifist in How to Train Your Dragon  

The Monstrous Nightmare is a dragon seen throughout the How to Train Your Dragon book series.

Physical Appearance

Monstrous Nightmares are styled rather devilishly, with two curved horns on their heads, and physically resemble a western-style dragon.

Nightmares vary in size, but can be the largest of the hunting dragons. They are rated as Size 3 in The Incomplete Book of Dragons, placing them in the same size category as small Riding Dragons such as the Chickenpoxer or Zebramount.

To note: The Incomplete Book of Dragons and the "Viking Dragons and Their Eggs" Info Page in How to Train Your Dragon give different stat numbers.


Monstrous Nightmares have excellent senses - eyesight, smell, and hearing. This makes them excellent hunters. They are intelligent and can speak Dragonese, as well as be rather devious. They have retractable claws and capable of breathing fire, making them one of the hardest and deadliest to train.

Behavior and Personality

Monstrous Nightmares are portrayed as rather selfish, vicious, and sly. They will immediately desert their master and flee for their lives when in danger, often leaving the humans defenceless to any oncoming threat.

Evidently there is some intra-species prejudice amongst Monstrous Nightmares. Though Fireworm and Killer dislike each other, Fireworm throws out a judgmental slur about Killer's lineage.

An aristocrat never growls. You must be one of those mongrel Nightmares. We pure greenbloods descended from the great Ripperclaw himself would never dream of doing anything so common.
  — Fireworm to Killer in Book 1  

Interesting to note, Monstrous Nightmares sided against humans during the Dragon Rebellion, abandoning their masters, as noted in The Incomplete Book of Dragons and How to Fight a Dragon's Fury.


How to Train Your Dragon

By unofficial Viking law, only the chief, or the son of the chief, can own one. Despite this, Snotface Snotlout, the nephew of the chief, acquires one named Fireworm, while Thuggory the son's chief from the Meathead Tribe owns another named "Killer".

Stoick the Vast has two hunting dragons, one a Gronckle named Newtsbreath and a Monstrous Nightmare named — interestingly — Hookfang.

How to Speak Dragonese

The individual Monstrous Nightmare, Fireworm, is briefly mentioned in this book. However, Nightmares in general are mentioned as well, as a food item for the Romans, particularly the Fat Consul.

In one corner of the room, the Fat Consul was having his tonsils tickled with a feather so he could vomit and fit in some more Monstrous Nightmare Crème Brulee and pudding.
  — Book 3  

How to Steal a Dragon's Sword

Another unnamed Monstrous Nightmare appears very briefly, actually acting heroically.

One hunting dragon went down in a blaze of flames, a Monstrous Nightmare belonging to Very Vicious the Visithug that sank its teeth into the neck of a much larger Grimwing, which then grabbed it around the throat, and snapping, biting, and screaming down they went, doomed, into the Gorge in a somersaulting ball of fire.
  How to Steal a Dragon's Sword  

The Incomplete Book of Dragons

Monstrous Nightmares appear in this reference book and in the 'Dragon Key' table at the back of the book.

How to Fight a Dragon's Fury

In the final book of the series, Nightmares are listed as one of the species that fought alongside Furious in the Dragon Rebellion.



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