Answer:
If you have it, you want to share it. If you share it, you don't have it.
My first is in wield, sever bones and marrow. My second is in blade, forged in cold steel. My third is in arbalest, and also in arrows. My fourth is in power, plunged through a shield. My fifth is in honor, and also in vows My last will put an end to it all.
White fat and fluffy, May even look like a puppy. Seems heavy but is light, Floats about without a worry, But if it turns dark you have to hurry!
Face with a tree, skin like the sea. A great beast I am. Yet vermin frightens me.
I can run but not walk. Wherever I go, thought follows close behind.
Almost everyone needs it, asks for it, gives it. But almost nobody takes it.