Answer:
Lovely and round, I shine with pale light, Grown in the darkness, a lady’s delight.
I start in little but I end in full, you'll find me in half and complete.
What has a neck and no head, two arms but no hands?
Take one royal word in the plural and make it singular by adding one letter
A
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.