Answer:
Useful tool for who in darkness dwell. Within you, corrupting like a deadly spell.
My tongue hangs out as I run over fields and streets all day. I get tied up every morning and untied at night.
It doesn't live within a house, nor does it live without. Most will use it when they come in, and again when they go out.
What is long and slim, works in light. Has but one eye, and an awful bite?
Always old, sometimes new. Never sad, sometimes blue. Never empty, sometimes full. Never pushes, always pulls.
What can never be put in a saucepan?
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?