Princess Luna was smiling as she entered the small dining area in the palace she shared with her sister. The moon was already rising and set on its course for the evening, the stars had been laid out and were slowly brightening in the darkening skies. Soon she would be traveling through her subjects' dreams again, picking up bits and pieces about the modern Equestria she still hadn't entirely acclimated to.
Her sister, Princess Celestia, was already dining as Luna entered. There was a sizable spread of varying delicious courses set out across the table. The sight and scent of the fresh salads, roasted vegetables, and assorted sweets and confections never failed to impress both of the princesses. The royal kitchens always did seem to overprepare. Celestia greeted her warmly, and together they shared a wonderful dinner, feeling every bit as close as the age-old sisters had ever been.
It wasn't until after most of the plates had been carried away by the staff that the wisp of greenish smoke drifted in through the window and with an audible pop, formed into a pair of scrolls in front of Princess Celestia. Luna smiled at her sister as she immediately opened the first scroll and began to read. Undoubtedly one of her little 'friendship reports' from Twilight Sparkle and another from one of her friends. Celestia always felt the need to read them first, without anypony looking over her shoulder.
The last of the food had been ferried away by their servants before Luna happened to notice the change in Celestia's posture. The pleasant and warm evening had previously shown in Celestia's body language, a deep calm suffusing her features and a relaxed happiness in her body. Now, though, there was a slight tension in her muscles, and even a slight shiver of... fear?
Luna only hesitated a moment or two before turning her head to address the two guardsponies at the door. "If I may have a moment with my sister."
It wasn't a question, and the guards quickly and curtly nodded their understanding before opening the door and stepping out into the corridor. A flash from Luna's horn and all three exits to the room were locked. Princess Celestia calmly set the letter down on the table, though Luna noticed that the scrolls were rolled tightly and re-bound already.
The silence hung in the air for a moment.
Princess Luna was first to speak. She had never been one to mince words or endlessly wait instead of taking action. "Sister, what has happened?"
Celestia closed her eyes, momentarily wishing she had some tea, or some other way of stalling for just a few more seconds. "One of Twilight's friends found the Mirror Pool."
Luna's eyes widened for just a moment. "The pool? Who?"
"Pinkie Pie."
Another silence hung in the air. Pinkie Pie was... difficult to handle in the best of times. Having two of her... "... What happened to the reflection?"
Princess Celestia took a deep breath before speaking, which never meant that anything good was coming next. "Her reflections summoned more. By the end there were dozens. All created with the desire to have fun with Pinkie's friends."
Luna winced. Dozens of copies with the intent to be with her friends would be overwhelming in any possible situation. The fact that the reflections were commonly... lesser than the original did not help. She knew the answer before she even asked the question. "They killed them, didn't they?"
Celestia frowned at the wording, but nodded slowly before speaking in a quiet, calm tone. "Twilight Sparkle found the emergency book in the library, and sent them all back into the pool. I wouldn't know if that was better or worse than killing them."
"It's the same." Luna's cold, detached voice allowed no dissension on this matter.
Princess Celestia stood and walked slowly around the table to sit next to her sister. Luna began to pull away, but as Celestia leaned in and crossed her neck over Luna's, the night princess sighed and allowed it, relaxing in the warmth of equine contact and sisterhood. Several long minutes passed with the two princesses simply resting in one another's company.
When Luna spoke again, her voice was very quiet. "They never allow the reflections enough time to grow into their own bodies and personalities."
"No, they do not."
A beat passed.
Celestia spoke again, her voice still calm though perhaps a bit guarded. "Twilight has sealed the entrance with a stone."
Luna nodded but did not move to break the embrace. Her voice was strained. "It is for the best."
The silence grew again, less comforting this time. Luna had a question on the tip of her tongue, and Celestia could easily read her dear sister. They alone could always tell what the other was thinking, almost without trying. They alone of all living ponies shared the kind of history they shared. After all, there had been a time when Celestia had been the only alicorn in all of the world, and then a long time when she and Luna had been the only two. Only recently had that changed, with Cadance's transformation.
After another few moments of silence, Luna spoke. Her voice was timid and fearful, more than it had been in over a thousand years. A millennium of doubt and uncertainty in her life and her relationship with the one pony closest to her spilled forth in a single question. "... Do you regret not doing the same?"
Celestia only shuffled closer in response, one wing spreading to cover her little sister's back as she pressed herself to her. She allowed the calming warmth of her body to fill Luna's heart before she spoke. "I have never regretted it," Celestia continued, and after only a half-second pause, "No, dear sister, not even then."
Luna's followup question had been answered before she could even pose it, and she could only offer a sad smile in response. After a moment, they both spoke in unison, quietly reciting the short spell that had brought Princess Luna into this world in the first place.
And into her own reflection she stared,
yearning for one whose reflection she shared,
and solemnly sweared,
not to be scared,
at the prospect of being doubly mared.