The Flightmare is a Mystery Class (originally from the Strike Class) dragon that appears in Dragons: Defenders of Berk. It is among the most terrifying and frightening dragons. It appears in the episodes Fright of Passage and in Maces and Talons Part I and Maces and Talons Part II.
The Flightmare is a medium-sized dragon that has a very ghost-like appearance. Its body is covered in tiny spots that almost resemble the night sky. It slightly resembles a mix between a Skrill, a Night Fury, and a Fireworm, with blue, glowing scales. It appears to get a bright glowing, ghost-like appearance from the glowing blue algae that is a stapled part of its diet.
From what has been seen, the Flightmare is a very aggressive and territorial dragon, being very protective of its territory and food sources. Seeing how Flightmares are build for speed and defense, they usually avoid fights with bigger and stronger dragons. Flightmares have been shown to be quite determined, as the Flightmare in Fright of Passage kept chasing his opponents, and was willing to search food over long distances. They seem to be quite reclusive and avoid contact with humans, unless they get in the way of their algae, or if they think that they do.
The Flightmare's body glows by eating algae that shines along with Arvindal's Fire, a type of the Northern Lights that can only be seen every ten years. Arvindal's Fire is a greenish blue, teal color. They can use this ability to nearly blind their prey or enemies.
The Flightmare can strike with a mist that paralyzes its prey to give itself enough time to return and finish it off. Its prey appears to have a glossy surface after being sprayed for a while. In order for the Flightmare to kill its prey with its mist, it needs to spray its prey for several seconds in order for it to freeze to death, for the temperatures reach below freezing.
Speed and Agility
Flightmares have shown to be fast and agile dragons, as the Hofferson's Bane in Fright of Passage was able to catch up with Toothless with ease. Even so, when Toothless was trying to get away from the Flightmare, it quickly boosted in front of him.
They have great stamina as shown by Hofferson's Bane, as it was able to fly long distances as it flew across the ocean to follow the glowing algae.
They can produce a loud banshee-like scream that can slightly affect other dragons, rather like a weak version of the Screaming Death. Also, the scream sounds like the one of Snow Wraith, only that the Snow Wraith has a little deeper roar.
Dragons: Defenders of Berk
A Flightmare known as Hofferson's Bane first appeared in Fright of Passage, terrorizing Berk every ten years during Aurvandil's Fire. Last time, Astrid's uncle, Fearless Finn Hofferson, faced the dragon and seemed to be frozen by fear, shaming her family's name. Astrid and Hiccup set out to find the Flightmare, where Astrid tried to fight it, but was frozen by the dragon's mist. They learned that victims of the dragon were not frozen by fear, but paralyzed. They soon discovered a stream of glowing algae that gives the Flightmare its glow, as well as other dragons (as discovered by Toothless). Realizing that the Flightmare only attacked Berk because it thought the Vikings were threatening its food supply, Hiccup, Astrid, and Fishlegs created a new channel for the algae to flow into the sea, and the Flightmare left Berk. Hiccup explained to the village what they learned about the dragon and that Finn Hofferson truly was fearless, restoring honor to Astrid's family.
Dragons: Race to the Edge
A Flightmare Heather had previously tracked down was the main desire of Viggo Grimborn in the episode Maces and Talons Part I and Maces and Talons Part II. The Dragon Hunters tracked it down to an island, possibly Algae Island which was found on Hiccup's map, and tried to capture it. With the help of the Dragon Riders the Flightmare managed to paralyze half of Viggo's men but was eventually captured. Later in the episode the Flightmare was muzzled and put in a dragon-proof cage. In the finale of the two part episode, it was revealed that Viggo wanted the Flightmare to access the emergency release for the Dragon Eye because they were at a lack of a Snow Wraith tooth for a key. When Viggo no longer needed the Flightmare he released it and it attacked Hiccup and Toothless. As soon as the Flightmare was released it, paralyzed Ruffnut, Tuffnut, Barf and Belch, Snotlout and Hookfang. Heather and Windshear came to the aid of the Dragon Riders and together they scared the Flightmare off but by then, Viggo was gone with the Dragon Eye.
Source: Dragons: Rise of Berk.
Titan wing Flightmares are purple with a faint, translucent blue outline. They have white and pink dots all over their wings. They still look similar to younger Flightmares, but their tail, which has a few spines on top, grew spines below too.
- It could be possible that the Hofferson's bane is the same flightmare that appeared in Race to the Edge, since Hiccup, Fishlegs and Astrid redirected the river and the algae into the sea, and flightmare followed it. Also, Heather said that she tracked the flightmare for months, so maybe she saw the same dragon that came from Berk.
- The Flightmare has been associating with many different classes. According to CartoonNetwork.com, it was in the Fear Class. The Dragon Tracker Part 3 special feature said that the Flightmare was a Strike Class dragon.  A promotional image for Defenders of Berk even said its class was unknown. However, Dragonpedia and the games has since confirmed that the Flightmare is a Mystery Class dragon.
- Many fans thought that the Flightmare made an appearance in the Dragon Manual in the first film. But it was later found to be, most likely, a Boneknapper.
- In order for the Flightmare to kill its prey with its mist, it needs to spray its prey for a few seconds longer than usual, such as it did with Fearless Fin Hofferson. Whereas people who are sprayed with mist for only a short period of time can still survive, like Astrid.
- The Flightmare is the only known dragon species that appears once every 10 years, at least on Berk.
- The Flightmare's design is similar to that of the Skrill, resembling that of Pelican Eels. Coincidentally, when it was first seen in the Defenders of Berk trailer, many fans thought it was a Skrill.
- It is the only dragon that glows other than the Fireworm, and both glow via eating something.
- The Flightmare is an omnivore, since its glowing algae diet consists of hundreds of tiny fish.
- The Flightmare is one of the five dragon species that doesn't have forked tongues. The others are the Woolly Howl, the Razorwhip, the Snow Wraith and the Snaptrapper.
- The Flightmare is now in School of Dragons as a dragon that can be obtained from the hatchery.
- The Flightmare that attacked Finn Hofferson made an appearance in Dragons: Rise of Berk and is now known as the Hofferson's Bane.
- It's glowing algae only glows every ten years around Berk, when Arvindal's Fire appears above the island.
- Almost all bioluminescent algae are marine based, which means that the Flightmare probably lived by the sea.