Answer:
It doesn't live within a house, nor does it live without. Most will use it when they come in, and again when they go out.
This thing all things devours: Birds, beasts, trees, flowers; Gnaws iron, bites steel; Grinds hard stones to meal; Slays king, ruins town, And beats high mountains down.
You seek it out, when your hunger is ripe. It sits on four legs, and smokes a pipe.
I climb higher when hot, But beware my rage, I’ll kill with a breath, If I can escape my cage
As beautiful as the setting sun, as delicate as the morning dew. An angel's dusting from the stars. That can turn the Earth into a frosted moon.
I am the fountain from which no one can drink. For many I am considered a necessary link. Like gold to all I am sought for, but my continued death brings wealth for all to want more.