Answer:
I am two-faced but bear only one. I have no legs but travel widely. Men spill much blood over me. Kings leave their imprint on me. I have greatest power when given away yet lust for me keeps me locked away.
Cold head and feet; round as a ball; always turning around myself.
The more of me there is the less you see.
I run up and down the stairs without moving. What am I?
With three leaves, I am just a plant. Add another leaf and everyone will want me for good luck. What am I?
I will disappear every time you say my name.