The Flightmare is a dragon that is medium-sized in length. Flightmare eggs are typically oval-shaped, and colored with bright neon colors, usually depicting the unborn individual's main scale color. The eggs grow brightly and are surrounded by a lingering glowing mist, possibly the same toxic substance used by Flightmares, emitted for additional protection.
The Flightmare is a very aggressive and territorial dragon. Flightmare's usually avoid fights with bigger and stronger dragons. Flightmares have been shown incredible determination and relentlessness, 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 and other dragons, unless they see anyone pose a threat to them or their food, in which case they will relentlessly punish the suspect.
- "Fire" Breath: The Flightmare can strike with a toxic mist that temporarily paralyzes the victim from head to toe, giving itself enough time to return and finish it off. The mist can be fired in blasts or streams, and vary in quantity, depending on the Flightmare tactics and size of the target. The mist leaves surfaces and victims glossy and slightly wet while the paralysis lasts. It seems to be very cold as Astrid shivered when she was sprayed by it. Large concentrations of Flightmare mist appear to kill their victims.
- Speed: Flightmares have shown to be fast and agile dragons, as the Flightmare in "Fright of Passage" was able to catch up with an average speed Nighty Fury like Toothless. When Toothless was trying to get away from the Flightmare, the Flightmare quickly flew in front of Toothless with ease. Although it might of been because of the glowing algae it ate to empower itself or at the fact the Flightmare saw Toothless' glow due to him eating the glowing algae and caught him, Astrid, and Hiccup by surprise.
- Banshee Roar: The Flightmare emits a loud, high-pitched banshee-like shriek that affects the concentration and stability other dragons in the near vicinity. They often combine their roar with their other abilities such as their glow to overpower their opponents, especially during their entrance and departure.
- Glowing Algae Dependency: The Flightmare owes one of its most powerful attributes to the glowing algae, and thus must be constantly near a source of it as the glow-enhancing effects last but a limited amount of time. Due to the scarcity of the algae the Flightmare must protect its main food source at all times from anyone who might try to consume even small quantities of algae in order to maintain its exclusive diet. Diverting the stream of algae will prompt the Flightmare to hastily purse it in fear of losing its food. Flightmares suffer the same effects as others when exposed to algae-enhanced glow, meaning they can be defeated by other Flightmares and dragons consuming glowing algae.