Good Riddles

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?

Question: You fill up a bathtub with water and you have a teaspoon, tablespoon, and fourth cup. What is the fastest way to empty the bathtub?

Question: Enter one hole and leave three,
once you succeed I'm on thee?

What am I?

Question: I am the beginning of the end, the end of every place. I am the beginning of eternity, the end of time and space. What am I?

Question: My shallow hills are the faces of kings.
My horizon is always near.
My music sends men to the grave.
My absence sends men to work.

What am I?