Answer:
The more there is the less you see.
I make billions of dollars selling windows. Who am I?
A single syllable do I claim black was my most famous name; Fetal to mortals here below thousands have I slain in a single blow.
I rise and fall no matter what, only at finals rest do I not budge. What am I?
What goes through towns and over hills but never moves?
What do you purposefully put lots of in and on your body, but run away from when you encounter it outside?