A wyvern is a large winged lizard with a barbed, venomous tail and sharp teeth. Like bats or birds, they have only four limbs, their forearms being wings, unlike dragons, which have six limbs--four legs and two wings. They have dark brown or grey bodies, around 15' (4.6m) in length, weighing around a ton. Although they have the strength and ferocity of dragons, wyverns lack the grace and intelligence which are innate to dragons, as well as the breath weapon natural to all dragons. Wyverns typically prey on deer, goats, and other such creatures. Unlike dragons, which can be sometimes good and sometimes evil, the wyvern is unambiguously malicious. They are not greatly intelligent, although they do speak Draconic. They are not averse to attacking anything less powerful than themselves.