The Deadly Nadder is very beautiful and bird-like: it is bipedal and possesses winged forelimbs and it is about the same size as medium-sized theropod dinosaurs such as Allosaurus. Its small yet keen eyes, equipped with poor binocular vision, are one of the tools it uses to stalk targets.
Its body is a vivid color, with a light beige underbelly, while its wings are mottled, darker shades. In front of its eyes is its curved nasal horn, which is often used to batter opponents; its lower jaw is shorter and wider than its upper, giving it an overbite. Ringing its skull are a set of long spikes. The tail is coated with a series of spines that can inject venom into a target, a feature it shares with other dragons such as the Whispering Death and the Screaming Death. When relaxed, its head spikes and venomous tail spines lay flat, and when alarmed, they are shot upward to intimidate its foe. The tail spikes can also be used to make a rattling noise which it makes right before it attacks, similar to rattlesnakes.
Titan Wing Deadly Nadders have more spikes on their head, back and feet. Their snouts are broader than normal Nadders' snouts. Their body is greenish with pink lines and they possess some blue spots on the wings.
The Deadly Nadder is one of the most beautiful dragons, and unfortunately, it knows it. It is well-known for its vanity; it constantly grooms itself to stay clean and maintain the luster of its scales.
Like the Night Fury, the Deadly Nadder is a picky eater whose diet comprises mostly of poultry and is allergic to domesticated hoofed animals. Nadders also eat a significant amount of fish and even graze on plants, as seen in the episode, "Crushing It". However, when it is trained, this dragon becomes very affectionate, not unlike a pet dog, pet cat, pet bird or other sociable creature. These dragons love to play fetch.
Deadly Nadders are also migratory, flying long distances to known nesting grounds to lay their eggs every year.
Approaching Deadly Nadders in their blind spots and scratching them under the chin is a surefire way to earn the dragon's trust, as is approaching from behind and gently smoothing the dragon's tail spikes down. Showing the dragons you mean no harm and that you are not so different from them is another way to earn a Nadder's acceptance.
The Deadly Nadder is possessed of very hot flame and venomous tail spines and teeth. Their flame is one of the hottest in the dragon world, second only to that of Fireworms. They are agile and quick in the air, an ability that is only enhanced when the dragon is given more chicken in its diet. Though they do not have great binocular vision due to the blind spot between their eyes due to their nose horns, these dragons have great hearing and are also quick and light on their feet. They are also classed as Tracking Class dragons due to their keen senses and their ability to find prey and people. They also were originally classed as Sharp Class Dragons, but this has since been reconsidered given their abilities.