The Silver Phantom is a species of Sky Dragon, though it is also referred to as an Air Dragon, first introduced in How to Seize a Dragon's Jewel.
As per their name, Silver Phantoms are the color of "the purest silver". They have huge wings for flying, a row of fairly long spikes down their backs, and a spaded tail.
The Incomplete Book of Dragons notes that this rare species has a small amount of dimorphism amongst the genders: females sport a single horn sprouting from their muzzles.
Silver Phantoms may also glow to some extent, or perhaps reflect light well to give the appearance of glowing, as seen in this passage:
- "Even though it was the dead of night, every silver scale was lit up and shone brighter than was strictly possible in real life. The Silver Phantom seemed to give off its own light, like the moon."
- ― How to Seize a Dragon's Jewel
The moon itself does not glow, but reflects light from the sun. Whether the author was making this comparison or that the glow was soft and silvery like we attribute to the moon, is hard to say.
Silver Phantoms are known to be the fastest and highest-flying dragons around, save, perhaps, for the Guardian dragons. They can also fly at the highest altitude, so high the air starts to thin. They are "very, very rare and very, very dangerous".
Silver Phantoms also have excellent sight, hearing, and sense of smell. The 'Dragon Key' at the back of The Incomplete Book of Dragons also indicates Silver Phantoms can produce electricity, and shoot lasers or missiles (unclear which).
Silver Phantoms also produce a lovely, lethal fire:
- "And as the dragon screamed, it poured out a jet of bright blue flames that blasted the trees in front of it, burning the leaves as bright as green stars before they dropped to the ground in powdery black smithereens."
- ―How to Seize a Dragon's Jewel
Silver Phantoms are very rare and highly prized as a Riding Dragon. Silver Phantoms are the fastest ride-able flying dragons known to Vikings, even faster than the Windwalker.
There are only two Silver Phantoms mentioned, including Valhallarama's riding-dragon, which is introduced in How to Seize a Dragon's Jewel. The second is found in The Incomplete Book of Dragons where Hiccup the First is seen riding a female.
Valhallarama's Silver Phantom is the first Silver Phantom introduced in the books. Valhallarama on her dragon, sneak up to Hiccup in the woods and attack him, not realizing he is her own son.
The Silver Phantom is detailed in this reference book, introducing Hiccup Horrendous Haddock I and his Silver Phantom. This dragon is also listed at the back of the book in the 'Dragon Key'.