Answer:
When it comes in, From sea to shore, Twenty paces you'll see, No less, no more.
Do what he says and you'll be fine, don't and you lose the game.
You can see nothing else, When you look in my face, I will look you in the eye, And I will never lie.
A circle of stones, never in rows. Stacked one on the other, mystery it sows. What is it?
Useful tool for who in darkness dwell. Within you, corrupting like a deadly spell.
You can always find me in the past. I am created in the present, but the future can not change me. What am I?