The Red Death is the main antagonist of How to Train Your Dragon.
The Red Death is a formidable dragon on the island which she and others of her kind consider home. Her appearance is similar to that of a Gronckle and possesses with six eyes (three on each side). This feature is shared with that of the deadly Nadder. Her tail is pegged with spikes, similar to that of a mace or chain ball. Her great wings allow her to take flight, despite her colossal size.
Unlike the other dragons, the Red Death appears to be truly evil and monstrous. She is the largest and most powerful dragon of all so she is able to easily overthrow and enslave the other dragons. The Red Death appears to be very ruthless and intolerant of failure as she eats other dragons that fail to bring back enough food. The Red Death appears to be untamable, unlike the other dragons. And it is unknown if it has any fear, being the largest and strongest. She is also extremly selfish as she didn't care about neither humans or other dragons.
The Red Death first appears when Hiccup, Toothless, and Astrid discover the Dragon's nest. After a Gronckle drops a tiny piece of fish to the Red Death, she emerges and devours the dragon. Then, the Red Death tries to eat Hiccup and his friends when she spots that Toothless has contributed nothing and has humans on his back, but they manage to escape. The Red Death then appears again when Stoick attacks the Dragon's nest. She attacks the vikings and destroys their ships in the process. Fortunately, Hiccup and his friends arrive and stall the Red Death while Stoick frees Toothless. Hiccup drives the Red Death into the clouds and conceals Toothless' form. Toothless fires several lightning blasts at the Red Death's wings but it doesn't harm the monster. Enraged, the Red Death shoots fire in all directions around her and manages to light Toothless' tail ablaze. Using as much time as they had left, Hiccup and Toothless lead the Red Death out of the clouds and allowed it to chase them until she attempted to fire a finishing blast. However, Toothless fired a lightning blast into its stomach and lit its insides ablaze. The dragon's wings are ripped apart, causing it to fall. In a resulting explosion, the Red Death is killed.
- The Red Death is currently the only antagonist to be killed in the How To Train Your Dragon franchise.
- The Red Death was the one who was responsible for the war between the Vikings and the Dragons in the Barbaric Archipelago.