What Am I Riddles

Question: Eight of us go fourth, not back, to protect our king from an attack. What are we?

Question: To many, I am life's source. I am also its most valuable resource. I create and burn my own precious element, and my destruction will be my punishment. What am I?

Question: I float when I am born, lay down when I am alive, and run when I am dead. What am I?

Question: People are scared of me but I am loved by some. I can be your best friend but could become your enemy in a blink of an eye. What am I?

Question: I break down buildings I crumble mountains You can't see me What am I?