Answer:
What has a ring but no fingers?
Soldiers fight it but never changes.
What has only two words, but thousands of letters?
What is part of you and all around you but if it entangles you, it will kill you?
What you become during a workout?
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.