This story is a sequel to For Want of an Egg
Centuries ago, Princess Celestia stole a dragon's egg to fulfill a prophecy, and found it necessary to deal with the egg's mother to keep said prophecy from being compromised. But now that the prophecy has been fulfilled, and her time as a princess is over, Celestia decided that it was time for the truth to come out.
It was also time for Celestia to face the consequences of her actions.