Answer:
This small creature kills even the largest one.
What does a cat have that no other animal has?
Dark, feathery, and popular in Baltimore and fantasy books.
I have eight to spare and am covered with hair.
What is that which, while it lives, constantly changes its habit, that is buried before it is dead, and whose tomb is valued wherever it is found?
You use it between your head and your toes, the more it works the thinner it grows.