Answer:
What letter comes next: O T T F F S S ?
I am the fountain from which no one can drink. For many I am considered a necessary link. Like gold to all I am sought for, but my continued death brings wealth for all to want more.
What goes in the water red, and comes out black?
What can go through glass without breaking it?
This is in a realm of true and in a realm false, but you experience me as you turn and toss.
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?