What Am I Riddles

Question: Without me, nothing exists. What am I?

Question: What has a single eye but cannot see?

Question: I'm light as a feather, yet the strongest man can't hold me for more than 5 minutes. What am I?

Question: One evening a man started to run. Then he turned left. Soon after, he turned left again. Then he started running home. When he got home there were 2 masked men waiting for him. Who were they?

Question: It brings light to a dark dark world,
In a current it travels and through tunnels it's hurled.
Touch it and it'll kill you.

What is it?