Elementals: the Quest

Here is your riddle: I am greater than god. I am more evil than the devil. The poor have me, The rich need me, And death comes to those who eat me. Who am I? *** I am ever hungry, And live if you feed me. I am never thirsty, And die if you quench me. What am I? *** I see much, but change little. I am firm, irresolute, Powerful, but gentle; I have enough strength to rip apart mountains, Yet be moved by gentle stirrings, I am life itself, And I give life to others. Who am I? Im a five letter word that has no end, One through three can amend, One, four and five are something alive, Two and three occur near thee. What am I? *** I am light as a feather, Yet no man can hold me for long. My presence causes life, My absence death. *** I welcome the day with a show of light, I steathily came here in the night. I bathe the earthy stuff at dawn, But by the noon, alas! Im gone. *** The last, but not the least, little one: Lighter than what I am made of, More of me is hidden than is seen, I am the bane of the mariner, A tooth within the sea. Speak my name.