Answer:
I get dirty when wiping things clean. What am I?
You heard me before and then again. Afterward I die, until you call me again. What am I?
I break down buildings, I crumble mountains but you can't see me. What am I?
I run smoother than any rhyme, I love to fall but cannot climb. What am I?
I cannot be other than what I am, until the man who made me dies. Power and glory will fall to me, only when he last closes his eyes.
Whoever made me don't want me. Whoever bought me don't need me. Whoever use me don't know me.