Answer:
I transfer oxygen from the atmosphere to your blood
I am filled with garb the price is free. Just return what you don't need.
What goes all around the world but never leaves its corner?
A dragon's tooth in a mortal's hand, I kill, I maim, I divide the land.
I start with an E end with an E and have a letter in me.
Give it food and it will live, give it water and it will die.