Answer:
It cannot be seen, it weighs nothing, but when put into a barrel, it makes it lighter.
They made me a mouth, but didn't give me breath. Water gives me life, but the sun brings me death.
I build up castles. I tear down mountains. I make some men blind. I help others to see.
Whoever makes it, tells it not. Whoever takes it, knows it not. Whoever knows it, wants it not. What is it?
Known to accessorize with feathers, trumpets, and harps.
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?