A Wyvern (also know as Wivern in different folklores) is a type of dragon with no arms. In place of those arms are wings, sometimes with small claws or "fingers" at the tip or middle of them. This creature is often mistaken as a bad omen. It is actually very rare and is considered a good omen and very lucky. They are usualy very high up on mountains, which makes them so rare. Wyverns are one of the largest species of dragons.
In detail, a wyvern ranges from 10 to 30 feet from ground to shoulders in height, the body is proportionate to it's height, has only two hind legs, wings as their second set of limbs, long neck the length of the body ending at a narrow shaped head with long snout that comes to a point, typically they are a lot like birds in that they use their set of legs to hold down prey and rip it apart with its mouth.
The wyvern was adopted as the symbol for the old English kingdon of Wessex. In Welsh myth, wyverns are enraged, like bulls, by the colour red. One hero threw a red rag into a river to distract the dragon, which he then shot with an arrow. Just like all dragons, wyverns have 'pits' behind their legs and mouth, where the scales are thin and easily punctured. These are the most vulnerable points on the wyvern.