Dishonesty
Disloyalty
Greed
Misery
Cruelty
Apathy
These are the Elements of Disharmony—sealed away, should the Elements of Harmony need to be stopped. There was a reason, after all, that the Element Bearers had all broken down at one point or another. The Elements of Harmony brought with them great power—but also a fantastical devotion to the Element. Should a pony defy their Element, or should it be denied to them....Celestia had already been forced to intervene once. She didn't know if she could fix everything when another one of them broke down. Again. It broke her heart to think she would have to destroy Twilight to remove the threat she posed—the Sun Princess hoped she wouldn't have to infuse the closest thing she ever had to a daughter with apathy. Twilight's enthusiasm, her devotion to anything and everything, was what defined her. If she wanted something, and you stood in her way, you'd best step to the side. Otherwise, you ain't gonna be standing much longer. Celestia could count the number of times she had feared—and one of them was when she had arrived in Ponyville to find the town in chaos. Is this what her student was capable of? Her student, so afraid of her she would cast a "Want It, Need It" spell to avoid disappointing her. She had been so proud to learn that spell, Celestia hadn't bothered to tell her it was illegal. Twilight Sparkle was devoted to the Princess, possibly more loyal to her than even Rainbow Dash, Bearer of Loyalty, could possibly be. The mare would sacrifice her life, a thousand lives, a million lives, for her, and that scared the crap out of the Princess of the Sun. Twilight was the most dangerous pony alive, and Celestia's own erstatz daughter. She would sacrifice millions if it meant saving Celestia, and not because she was asked—because she wanted to. She would do it without a second thought—if she had arrived at so drastic an act, it was surely the only way, the best possible option out of a universe of decisions. Celestia wasn't even sure if she valued her friends higher than she valued the Sun Princess.
What hurt more was that she didn't want to know the answer.