Answer:
It is greater than God and more evil than the devil. The poor have it, the rich need it, and if you eat it you'll die.
Five hundred begins it, five hundred ends it. Five in the middle is seen. First of all figures, the first of all letters. Take up their stations between. Join all together, and then you will bring before you the name of an eminent king.
What moves without seeing and cries without eyes?
Hard to catch, easy to hold. Can't be seen, unless it's cold
I sleep by day, I fly by night. I have no feathers to aid my flight.
You use it between your head and your toes, the more it works the thinner it grows.