What Am I Riddles

Question: I can hurt and make people bleed when I'm on the dark side, but used in good ways and I can also help you. What am I?

Question: What is as ancient as the earth but new every month?

Question: I am a nice word composed of five letters, but the Romans would call me a numbers.

What am I?

Question: I am longer than trees I am longer than earth ...but lower than grass What am I?

Question: Swallowing one is fine.
Swallowing two together is fine.
But Swallow them separately and all shall fall.

What are they?