Answer:
I am the ultimate killing machine used not once but TWICE I can be made by humans.
Golden treasure I contain guarded by hundreds and thousands. Stored in a labyrinth where no man walks Yet men come often to seize my gold. By smoke I am overcome and robbed then left to build my treasure anew.
What goes through a door but never goes in and never comes out?
I am constantly overlooked by everyone but everyone has me. What am I?
The warmer I am, the fresher I am. What am I?
I always have to work with something in my eye. What am I?