Answer:
Curtail me thrice I am a youth; behead me once a snake; complete I'm often used in truth when certain steps you'd take.
I am black of eye and bright of hair. I fast into the ground and follow my lord as he races around the world. What am I?
I help you carry your books.
I drive men mad for love of me, easily beaten, never free. What am I?
I have thirteen hearts but no body or soul. What am I?
I am your mother's brother's only brother in law. Who am I?