Answer:
Turns me on my backs and open up my stomach. You will be the wisest of men though at start a lummox.
A single syllable do I claim black was my most famous name; Fetal to mortals here below thousands have I slain in a single blow.
What has a head and a tail, but no body or legs?
It rows quickly with four oars but never comes out from under its own roof. What is it?
By Moon or by Sun I shall be found. Yet I am undone if there's no light around.
What do you purposefully put lots of in and on your body, but run away from when you encounter it outside?