If you knew you should have treated somepony differently, would you have?
Princess Celestia asked herself many of the questions she hated most. The bright side of this was that she didn’t have to answer them. When luck was kind, she even had the opportunity to be caught up in everything that would allow her to forget intrusive barbs like that.
Cruelty in her thoughts was to be combated (and that in itself could prove to be a nasty word) with kindness in deed. Chances for repetition could be dulled by working at something new, thus weakening something old. It’s what she had tried, anyway. The chance for somepony else’s happiness by doing something simple and alleviating wasn’t ever worth forgoing.
The mirror before her stood, heavy and gleaming. Within the flawless surface, her own face dared to reflect tiredly back at her. Many gems glinted proudly, boasting the mirror’s many secrets and only outshone by Celestia’s mane. The tiny image of a pony prancing in a miniature mirror crowning the grand old thing was the chief insult.
Many years ago, Celestia had re-examined the artifact and the luminous surface that held endless new ways to haunt her. Before the Everfree castle, there had been another, and she had hauled this old artifact of the gods from the ruins. It was the only thing she bothered taking. One trip to the other side had been enough for her to know the seemingly indestructible piece was worth monitoring as it went through its cycles of opening and closing.
Now, all it did was present her with a crystalline barrier that had claimed her Sunny. A whole world could be found on the other side, when the cycle was right. There was no telling where Sunny could have ventured or what could have happened to her, and certainly not after the time it took to realize that this was the artifact Sunset Shimmer had trifled with. There had been no train tickets purchased late in the night when she left or airships that held a stowaway barely trotting into her teen years. Gifted Unicorn School friends hadn’t smuggled Sunset to one of their homes on the date of what became their last quarrel because Sunset didn’t have any friends.
Over the years, the mirror never appeared to gather dust, no matter how many layers of old sheets the princess threw over the thing. Before, she locked it plainly, keeping it covered and out of sight with other magical artifacts of middling concern, where castle staff were informed make detours around. Before Sunset’s hurtful stunt, the only one Celestia really had to hide the mirror from was herself, especially because she had never thought Sunset Shimmer had really found this particular artifact the few times she had referred to a 'magic mirror'. Every filly had a very active imagination, and Princess Celestia could not see why one little filly with an attitude that burned would be any different. Especially not when she was surrounded by furnishings fancy enough to look magical, even when they were no more than elegant, well-made pieces to bring life to the castle's interior.
Now, all she could think about was the subtle malice to it. Her knowledge of its nature was useless, and despite the increasingly secure places she locked it, she was aware that it was dangerous. A greater field of protection against those who would seek to exploit the artifact’s power became an advancing priority in her thoughts.
(And who would keep what was little else than the tomb of Sunset Shimmer?)
Yet the princess hadn’t come here for mourning to snag at her mind and produce such gloom. She had come to this dusty old space because she knew Cadance needed a wedding gift. An old mirror with such a fantastic look would easily be appreciated by the mare and a welcome addition to any new home. She couldn’t help but find something brighter and kinder in the idea of giving somepony a gift which they could protect and value so highly. A treasure – if Cadance chose to think of it so – that wouldn’t break when anything else might.
Sunset Shimmer hadn’t even been the one initially in Princess Celestia’s thoughts when that question had sprung to mind.