Answer:
The sharp slim blade, that cuts the wind.
Weight in my belly, Trees on my back, I travel fast in my place, but feet is a feature I lack
Two in a whole and four in a pair. And six in a trio you see. And eight's a quartet but what you must get. Is the name that fits just one of me?
What is it that makes tears without sorrow and takes its journey to heaven?
What is it that has four legs, one head, and a foot?
Almost everyone needs it, asks for it, gives it. But almost nobody takes it.