Answer:
Who keeps the ocean clean?
I fly yet I have no wings. I cry yet I have no eyes. Darkness follows me. Lower light I never see.
With three eyes and as black as night I frequently knock down ten men with a single strike!
There are four of us but it seems like everyone loves spades the most.
I sit high glowing and watch the world go by. Without me everything would seem dull and dangerous. What am I?
I am rarely touched but often held. If you are smart you'll use me well. What am I?