Celestia's death

Princess celestia died when her sister stabbed her in the middle of the night. Now nightmare moon has taken over Equestria and had destroyed the elements of harmony, so now the mane six can't do anything about. Nightmare moon has changed all the rules, imprisoned shining armor and cadence and use earth ponies as slaves . Can the mane six save Equestria without the elements of harmony or they'll live like this for the rest of their lives? Read to find out