Answer:
Marking mortal privation when firmly in place. An enduring summation inscribed in my face.
I can be thin but not fat; in your body but never on your placemat. I'm always better when I'm fresh but you'll never see me in the flesh.
I'll bring out your bulls and slow your roll. I may even come out of your skull.
I am a shimmering field that reaches far. Yet I have no tracks and am crossed without paths.
What always ends everything?
A little house full of meat, no door to go in and eat.