Answer:
A precious stone, as clear as diamond. Seek it out while the sun's near the horizon. Though you can walk on water with its power, try to keep it, and it'll vanish in an hour.
What has six faces and twenty-one eyes?
A building where people and stories are on stage
Look into my face and I'm everybody. Scratch my back and I'm nobody.
I'm not man's best friend, I'm their enemy, I can mark your end, yet you do not see me, I am very small, but very tough, If you have me, then you have it rough.
Break me and I am better immediately set and harder to be broken again.