It was a happy day for her, that much she knew. Everything that she’d been hoping for these many long centuries had finally come true. Princess Celestia, the one who raised the sun in the sky, was, on this day, no longer the sole ruler of her nation. For today was the day that her beloved sister, Princess Luna, had returned from her thousand year imprisonment on the moon. Although no pony alive today was old enough to recall the times when there were two Princesses in their world, they’d nevertheless accepted her gladly, a fact which Celestia had appreciated.

There had been celebrations and welcomings for Luna as she returned, but for Celestia, she was merely happy that she had her family back again. The pain she’d felt over this long thousand years had been almost unbearable, but now, both she and her sister finally had a chance to undo those centuries of distance between them. Right now though, the sun Princess was enjoying this calm and peaceful moment. She was sitting on a large, purple cushion in her royal chambers, next to a warm and roaring fire, relaxing after the day’s long celebrations.

Under normal circumstances, she might be busying herself with some matters of state, perhaps a petition to look at or some new treaty to sign. But right now, she was content to be reading a personal letter. Though this was no mere letter, but a correspondence from Celestia’s prized pupil, the mare who had been responsible for bringing her sister back to her. Twilight Sparkle. The young mare was, without a doubt, the most talented user of magic of her generation. The only one who had ever come close was Celestia’s one-time student, Sunset Shimmer, though the Princess had often tried to forget the pain she’d felt at what she perceived as a failure on her part to tutor that mare properly.

Twilight had proved to be adept at virtually every school of magic Celestia had taught her, and her eagerness to learn was always heart-warming to her. Nevertheless, she’d also become a close friend to her, having known Twilight since she was but a filly. Recently, that union had saved her, as it was Twilight’s dedication to Celestia that had urged her on, driving her forward to undo the terror that Nightmare Moon had attempted to unleash on Equestria. With the aid of her new friends, Rainbow Dash, Fluttershy, Applejack, Rarity and Pinkie Pie, Twilight had rediscovered the elements of harmony, and through them, made their world right again.

Right now though, Twilight was doing her best to adjust to her new home, the tiny village of Ponyville, which was what this letter to Celestia entailed. Smiling, Celestia read her student’s letter, hearing about how the residents of Ponyville were being very welcoming to her and how much fun she was having there. It pleased her to know that she was doing well, but her train of thought was interrupted by the unmistakeable sound of her door creaking open. Her head turned in that direction and a smile formed on her face as she saw that it was none other than her sister, Luna, who was now entering her chambers.

The younger Princess smiled at her elder sibling and nodded in greeting towards her, which Celestia promptly returned. Luna walked near her sister before sitting herself down on a similar cushion to the one Celestia was resting on. The two sisters enjoyed this quiet moment together in silence for a few moments, but even though the two had not seen each other in many years, Celestia still knew her sister well enough to know that something was on her mind. She waited for her to speak for herself however, and it was not long before Luna broke the silence.

“That young unicorn, Twilight. I am truly grateful to her for freeing me”.

Celestia smiled at that.

“As am I. She did what I never could, and thanks to her, I have my family back”.

Luna smiled at her sister, a sight Celestia once feared she’d never see again. But that smiled faded a little as Luna appeared to be deep in thought. After only a few moments, she spoke again.

“Tell me, sister, you have plans for her…don’t you?”

The smile now faded from Celestia’s face also. Her younger sister was no fool. She would have known, after meeting Twilight and learning that she was Celestia's personal protégé, that the elder Princess had something very important planned for her. Nopony would ever get that position if there was anything less in mind for them. In response, Celestia merely nodded, a gesture which Luna replied to with a thoughtful glance. Celestia did not blame her for thinking hard on the matter. After all, she herself had been considering the possibility for many years now, as this was not something to be taken lightly.

"Has this happened before?" Luna asked.

Celestia nodded again.

"Yes. Some years ago, I encountered a young pegasus filly named Cadence. She experienced a very difficult trial in her life, and through it, she became as we are. After that, I adopted her as my niece".

Luna's eyes widened at that with surprise. Celestia chuckled a little.

"I'll be sure to introduce you two at some point, I'm sure you'll like her."

The moon Princess considered that for a moment before nodding. Celestia knew her well enough to know that this would have been a difficult thing to accept. After all, when last she walked upon this world, Luna and Celestia had been the only ones of their kind in existence. Now, after so many centuries, not only was there another like them, but a fourth was already in the works. It was a difficult fact to accept, and even Celestia had taken a while to truly embrace it. After all, she had walked this world as the only one of her kind for many centuries. To have another appear like that, one she had not even met prior to her change, was a shock to be sure. But even so, the sun Princess had been happy, if only because she was no longer alone.

After a long silence had fallen between them, Luna broke it once more.

"I am grateful to what Miss Sparkle did for me. It is a debt I doubt I can ever repay. And to wield the element of magic...that is truly a feat worthy of story and song. But...ascension? Are you certain?"

Celestia nodded.

"Indeed I am. When I first met her, she was in the middle of one of the largest bursts of magic I had ever witnessed in a unicorn for many years. Certainly more than any filly her age should have been able to conjure up. So powerful was she that her power even hatched a dragon egg".

Luna seemed surprised at that, and Celestia knew why. Aside from unicorns, dragons were probably the most magical beings in their world. For a filly to have caused one to hatch, when all others had failed to influence it at all, was a level of magic almost unheard of. Celestia's mind cast her back to that fateful day. The day she met Twilight. The poor girl had been so terrified of what she'd done, what she knew she was now capable of. If it had not been for Celestia's reassurances, she might have been so terrified that she would have sworn off magic entirely. Thankfully, the Princess had allayed those fears, and helped her grow into her powers as the years passed by.

"There were problems, of course. Twilight was always so dedicated, so utterly transfixed on her magic, that everything else became secondary to her. Aside from myself, her family, and the young dragon she raised, she seemed most unwilling to make friends. She became practically isolated from all pony contact, buried in her work, her studies, even in spite of my efforts to make her see the value of such relationships. There was a time when I even feared she might have..."

The elder Princess turned away, hiding her face from her sister.

"...might have followed in other ponies' hoof-steps".

Luna looked confused at her sister's behaviour when she said that. Celestia had yet to tell her of her past pupil, and her similar failure to teach those important lessons. She would tell her that tale one day, but not today. The elder sister faced her once more and gave a warm smile.

"But going to Ponyville has done something I never seemed to be able to do for her. It has opened her heart to others. The friends she's made there have helped her grow into the mare I always knew she could be. And I could not be happier for her choice to now live there. The ponies she has met, they will help her, teach her more of the magic of friendship, even though they may not realise it."

Luna considered that for a moment before letting out a long sigh, returning her sister's smile as she did so. It was clear that there was still some hesitancy on her part to go ahead with this plan of Celestia's, but for now, she seemed to have accepted it, which was something the elder sister was grateful for. Celestia meanwhile had faith in her plan for Twilight. She knew deep down that she would succeed where Sunset had failed. Her ability to wield the elements was proof enough of that. And if she continued on this path she'd set for herself, then Celestia knew that Twilight would one day reach heights that the young mare did not even know were possible for her. Celestia was brought out of this thoughtfulness by her sister's voice.

"Then you are sure? That Twilight will be ready?"

Celestia smiled at her newly-returned sister and nodded.

"Trust me, Luna. When the day finally comes when Twilight achieves that great change...she will be".