Answer:
This thing runs but cannot walk, sometimes sings but never talks. Lacks arms, has hands; lacks a head but has a face.
Long and slinky like a trout, never sings till it's guts come out.
Scythe of darkness, Shadow’s light. Guiding eye of thirteenth sight.
When you stop and look, you can always see me. If you try to touch, you cannot feel me. I cannot move, but as you near me, I will move away from you.
Kills the bad ones and the sad ones. Tightens to fit, so one size fits.
What did the piece of wood say when he saw the screwdriver and screws approaching?