Answer:
I dig out tiny caves and store gold and silver in them. I also build bridges of silver and make crowns of gold. They are the smallest you could imagine. Sooner or later everybody needs my help. Yet many people are afraid to let me help them.
I'm the source of all emotion, but I'm caged in a white prison.
What is bought by the yard by is worn by the foot?
What is it that given one, you’ll have either two or none?
My first is in wield, sever bones and marrow. My second is in blade, forged in cold steel. My third is an 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.
I always have to work with something in my eye. What am I?