Princess Celestia, the princess (or Technical Queen) of all Equestia, is a seemingly happy and calm benevolent ruler of Equestia, and happily respects the opinions of her subjects. She's not even bothered by the crude rumors of her being a tyrant, a molester, or even the unfortunate nickname of "Trollestia." However, she does have a great deal of personal pain that even Twilight Sparkle has thought to be long dealt with. Celestia is still sad that she banished her sister to the moon when she was Nightmare Moon, intending on turning her back to normal. Though that is long since dealted with by her redeemer, Twilight, Celestia is still saddened by it, which makes her vulnerable to a treacherous spirit of Nightmare Moon, now a shadowy nightmare demon ghost, who tricks Celestia into believing that Nightmare plans to create the Elements of Disharmony with five ponies (and a griffin) in contrast to her student and her friends. Celestia, falling for it, goes on an innocent, but blind hunt for those who are contrasts of the Elements of harmony, not aware of the Nightmare spirit's true intentions. (Spoilers for following chapters not intended.)

note: i am not a very perect speller, so don't exsect this to be a million dollar perfetion.
it is compination of tragedy, saddness, dark, with little bits of comedy everynow and again (sorry for that, i am mostly a comedian.)
Credit for Image belongs to johnjoseco.