Answer:
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.
I can be written, I can be spoken, I can be exposed, I can be broken.
You heart it speak, for it has a hard tongue. But it cannot breathe, for it has not a lung.
You use a knife to slice my head. And weep beside me when I am dead.
The higher I climb, the hotter I engage. I cannot escape from my crystal cage.
What language does a billboard speak?
Difficult
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?