I’m not quite a ferret and farther from a goat. Ignore the Inscryption, I’m merely a. . . What am I?

I can bring great fortune if a rare one is found, but I cannot survive long when out of the ground. People use me to to keep livestock around.

I can be found in a deep underground place, smothered in my dark friend’s cold embrace. I’ve sparked imaginations, I’ve made people squeal, but at the end of the day, I’m still not real. What am I?

I have no face, yet nonetheless I watch with two bright eyes: one that blinks with every month and one that never dies. I often shroud myself in grey and mourn for those who sleep; my tears and and cries of anguish flow as often as I weep.

Feed me to fire and I'll melt down your knife. Eat me or quench my thirst, I might save your life.