Answer:
What dress does everyone have, but no one wears?
Useful tool for who in darkness dwell. Within you, corrupting like a deadly spell.
I pass before the sun, but make no shadow.
What goes through a door but never goes in. And never comes out?
When the day after tomorrow is yesterday. Today will be as far from Wednesday. As today was from Wednesday. When the day before yesterday was tomorrow. What is the day after this day?
When is it bad luck to see a black cat?