Medium simple riddles with simple answers

I build up castles. I tear down mountains. I make some men blind, I help others to see. What am I?

They are twin sisters, same height; they work in the kitchen, arm in arm. Whatever is cooked, they always try it first.

You measure my life in hours and I serve you by expiring. I'm quick when I'm thin and slow when I'm fat. The wind is my enemy.

Never trust this fellow’s grin. His teeth are sharp and course, his blood’s as cold as icicles, and he’ll show no remorse! What is it?

I am a fruit. Remove my first letter, it's a crime. Remove my first and last letter, it's a kind of music. What do you think am I?

Poke your fingers in my eyes and I will open wide my jaws. Linen cloth, quills, or paper, I will devour them all. What am I?

What am I?

What goes up and doesn’t come back down?

I have cities, but no houses. I have mountains, but no trees. I have water, but no fish. What am I?

I can run, but not walk. Thought is not far behind me. What am I?