Answer:
A certain wizard resided in a city made from this gemstone.
Always old, sometimes new. Never sad, sometimes blue. Never empty, sometimes full. Never pushes, always pulls.
What does a WW1 Trench, A Submarine and a Popular Phone App all have in common?
It happens when something has been cut with H2O.
What is that which, though black itself, enlightens the world without burning?
You use it between your head and your toes, the more it works the thinner it grows.
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?