What Am I Riddles

Question: A thousand wheels, but move I do not.
Call me what I am, call me a lot.

What am I?

Question: I cannot be seen, cannot be felt,
Cannot be heard, cannot be smelt.
I lie behind stars and under hills,
And empty holes I fill.
I come first and follow after,
End life, kill laughter.

What am I?

Question: All things I devour: Birds, beasts, trees, flowers.
I gnaw iron, bite steel.
I grind hard stones to meal.

What am I?

Question: I have no heart Yet I can live Even if I have fallen Fires are my enemy You are my enemy

Question: im fast and slow I go everywhere you go yet you cannot see me im in tree's in the sky in plants and in your body pretty much you need me to survive what am I?