The LORD said unto Moses, Fear him not: for I have delivered him into thy hand, and all his people ... So they smote him, and his sons, and all his people, until there was none left him alive: and they possessed his land. Numbers 21:34
Trivia: What was the booty that the Israelites got from the Midianite massacre?
What the Bible says about Cryptozoology
Not much is known about this creature, except that he could talk and was the most clever ("subtil" in the KJV) of all of God creatures.
Now the serpent was more subtil than any beast of the field which the LORD God had made. And he said unto the woman.... Genesis 3:1
And he could walk as originally created, because later he was forced by God to crawl on his belly and eat dust as a punishment. The Bible doesn't say what he ate before God punished him.
And the LORD God said unto the serpent, Because thou hast done this, thou art cursed above all cattle, and above every beast of the field; upon thy belly shalt thou go, and dust shalt thou eat all the days of thy life. Genesis 3:14