Answer:
This thing all things devours: Birds, beasts, trees, flowers; Gnaws iron, bites steel; Grinds hard stones to meal; Slays king, ruins town, And beats high mountains down.
Three lives have I. Gentle enough to soothe the skin. Light enough to caress the sky. Hard enough to crack rocks.
The man who invented it doesn't want it. The man who bought it doesn't need it. The man who needs it doesn't know it. What is it?
You use it between your head and your toes, the more it works the thinner it grows.
I can run but not walk. Wherever I go, thought follows close behind.
Iām grown from darkness but shine with a pale light. Very round I am and always a lady's delight.