Answer:
My first master has four legs, my second master has two. My first I serve in life, my second I serve in death. Tough I am, yet soft beside. Against ladies cheeks I often reside.
I build up castles. I tear down mountains. I make some men blind. I help others to see.
Lighter than what I am made of, More of me is hidden Than is seen.
What has a big mouth, yet never speaks?
Late afternoons I often bathe. I'll soak in water piping hot. My essence goes through. My see through clothes. Used up am I - I've gone to pot.
What is always coming but never arrives?