Answer:
A dragon's tooth in a mortal's hand, I kill, I maim, I divide the land.
Vikings use this for warmth.
How far will a blind dog walk into a forest?
Late afternoons I often bathe. I'll soak in water piping hot. My essence goes through. My see through clothes. Used up am I - I've gone to pot.
It's been around for millions of years, but is never more than a month old. What is it?
It's what light turns into in the night