A wivern is a two-legged dragon with wings and a spiky tail. Medieval literature often features stories that include the mythical wivern.
While the wivern is a frequent character in legends and stories from the Middle Ages to contemporary fantasy novels, it's probably most often found in British coats-of-arms and crests. These symbols and designs were found on helmets, shields, and other parts of a feudal knights' armor. A wivern might represent a soldier's family, town, or state. You can also spell it wyvern — either way, the root of the word is the Old French guivre, "snake."