A large, fearsome dragon-like creature, traditionally having two legs, wings, and a serpentine tail. A wyvern who lived near the Wye River in the West Country battled with Sir Cadogan in the 11th century. The wyvern nearly won, eating Cadogan’s horse, melting his helmet, and breaking his wand. However, the knight returned to the fray mounted on a fat grey pony and managed to spear the tongue of the beast with his broken wand, which caused the wyvern to explode (Pm).
wyvern = a legendary creature with a dragon's head and wings, a reptilian body, two legs, and a tail (Wikipedia)