The Deadly Nadder is a species of dragons, said to be one of the most beautiful. They are well known for their poisonous spines
In appearance, the Deadly Nadder is very bird-like: it is bipedal and possesses winged forelimbs and they are about the same size as medium sized theropod dinosaurs such as Allosaurus. Its small yet keen eyes, equipped with binocular vision, are one of the tools it uses to stalk its targets. Its body is a vivid blue in color, with a light beige underbelly, while its wings are motted with yellow, orange and blue. In front of its eyes is its curved nasal horn, which is often used to batter opponents. Ringing it's skull are a set of spikes. Coating the tail is a series of spikes that can inject venom into a target. When relaxed, its head spikes and venomous tail spikes 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.
In terms of behavior, the Deadly Nadder is fast and dangerous, though its potency as a hunter is hindered by the blind spot directly above its nose (possibly due to its large horn). As a result, the dragon relies on its keen sense of smell, often instead of its binocular vision, in order to find its prey. The Deadly Nadder also has at its disposal its tail spikes, which are used as projectiles to stun or immobilize its prey. Its most devastating trait, however, may well be its ability to blow magnesium-fueled flames, which can easily melt metal. The Deadly Nadder is also 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.
The official Website describes Deadly Nadder as follows: "One of the most beautiful dragons in the world is the DEADLY NADDER. It is easily recognized by the bright blue body and brilliant yellow spikes that cover it head to tail. This colorful dragon is active any time of the day or night. Nadders are quick and agile in the air and can fly for long distances, but will almost always land before attacking. Nadders travel and raid in groups, making them especially dangerous. The Deadly Nadder isn't the largest or fastest dragon, but it possesses the hottest fire in the dragon world. The blast of a Nadder can melt steel, or turn a man to ash in seconds. But the dangers of the Nadder don't stop there. The tail of the Nadder can be whipped around, releasing a volley of giant spikes that can penetrate trees, walls, and Vikings."
"A tropically hued fellow who is nastier than he looks. "He or she has raptor-liked tendencies and is very alert," DeBlois says. "He or she is also highly curious and aggressive." The Nadder can attack in two ways: Breathing a super-hot fire made of pure magnesium across hundreds of yards, or shooting off spikes from its tail."
- A Deadly Nadder made a brief appearance in the Dreamworks short Almost Home, though it was just it's foot.