Answer:
The thinkers usually hold this body part
Where can you add 2 to 11 and get 1?
What is the end of everything?
What devours all and can kill a king. Destroy a town and crushes mountains down?
Handy when you need to measure something or run a kingdom.
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.