A few minutes turned, and life wasn’t so easy anymore.

“It’s time to put our differences behind us, Luna. Will you accept my friendship?”

Life had become strange, full of doubt and uncertainty.

“I'm so sorry! I missed you so much, big sister!”

“I’ve missed you, too.”

It was what she was supposed to say. What “Princess Celestia” would say.

She wasn’t even afraid, the way she was when she saw the impossible rainbow in the night sky. When she recognized the magic of Harmony, and knew Twilight Sparkle had been right after all.

Celestia had winged over with all speed, mind reeling. Maybe Luna was gone again, and all would be as it should be. Maybe she was Nightmare Moon, and a new battle would come.

Her ill-used wings were pained by the short flight, and that endless, dull headache had grown worse. Celestia had felt so frail. She wondered if she could even defeat Nightmare Moon if it came to a fight.

Instead, something else happened. She arrived to find Luna, stumbling to the old castle’s floor. Not Nightmare Moon, but Luna. Curled up, dazed and crying, with every bit of the old horror cleaved from her soul.

Celestia’s eyes turned to the side as they hugged, mouth grimacing from its gentle smile.

One thousand years since they parted. Years Celestia spent moving on, piecing together her lonely, perfect life. Everything had finally been in order. Everything finally made sense.

And here was Luna. Haunting her once more, shattering her long-built normalcy. Unasked for. Unwanted.

But she couldn’t say that. “Princess Celestia” would not say that, no matter how much it grated to see the world spiral back out of control.

She smiled, serene and mature as Ponyville celebrated around them. She kindly gave Twilight leave to remain with her new friends, and watched Luna play with the foals.

The white lips fell to a gentle, more genuine smile. This… this would be alright.

Celestia nodded, the last vestige of her old fears falling away. The world had changed, yes, but she could work around it. Luna was a problem that could be solved. She needed companionship – ponies to keep her entertained, to make her feel loved. These could be assigned from the castle staff, at least until she made her own friends. She would be happy, and Celestia could move on.

The smile faded. Something about these thoughts felt… “wrong,” though Celestia couldn’t say why.

After a second’s thought, she shook her head. They were not wrong. It was all for Luna’s sake, after all. Celestia cared for her.

Do I?

She mused the thought another moment, and came to a pleasing answer. I want Luna to be happy. If that isn’t “caring,” then what is?

Luna kept sending her glances. They were nervous little looks that quickly shot away, like a guilty child’s. She knew there were words yet unspoken between them, and they would be difficult words.

Celestia smiled warmly back, drawing a weak grin from her sister. Don’t worry, Luna. It’s okay. It’ll all be okay.

I’ll take care of everything.

As the sky became red, Luna forgot her fear. She turned to the west, taking in the wonder of the setting sun.

She loved the dusk – better than the day, better even than her own night. It was when the sky ceased to be predictable. Not boring, uniform blue or black, but a riot of reds that changed from minute to minute, growing all the more vivid as they disappeared. There would be other dusks, but each was different. Each was beautiful.

Her face lit with joy as the orange rays danced above her head. Luna had missed this. Her time on the moon had passed without notice, but she missed this all the same.

It was encouraging. The thousand years had doubtless left little untouched, both of Equestria and the world beyond. Yet the dusk remained, smiling down like it had waited for her. Assuring Luna that though much had changed, some things had not.

A gold-shod hoof settled gently on her shoulder. Luna looked up, and smiled as bravely as she could.

Her sister had not been unchanged. Tia was older, and walked more slowly than she used to. She had been withdrawn throughout the party, but… well, she had to be as scared as Luna was. The coming talk would not be pleasant for either of them.

We’ll get through it. Together.

Luna approached the chariot with a spring in her step, heart lightened by the vivid sunset. She waved happily as Twilight said goodbye, calling out a cheerful promise to visit.

She was still scared, it was true. Of what Celestia would say when they were finally in private. But she did not think Tia would punish her, or yell at her, or any of those other things she could rightfully do. The older sister was calm, her smile serene and kind as the chariot rose to the sky.

It really seemed like Tia forgave her. Like a big sister should.

The smile on Luna’s face grew brighter. Big sister. That was another thing she really, truly missed.

Her fear slowly returned as they came to Canterlot, landing in a discreet courtyard. With long shadows all around them, Celestia wordlessly led her through the twisting, darkened hallways of the castle at nightfall.

Luna wanted to stop and look. This was her first time here, and the new castle seemed so large compared to the old one. There were signs pointing to justice halls and libraries, and places with names she didn’t recognize. But Tia kept silently striding forwards, and Luna uttered not a peep as she scrambled to keep up.

By the time they came to Celestia’s parlor, Luna’s hooves were trembling. She was scared again.

At least the room was well lit, and had a homey air to it. A grandfather clock sat atop the ink-stained carpet, offering a rhythmic tone to combat the silence. The parlor had a few sofas, though was dominated by a massive, gilded desk, upon which sat reams of paper in several wicker trays. It all looked worn and used – a far more comforting sight than the pristine halls.

Celestia sighed lowly, as if steeling herself, and gestured to a couch. “Let’s sit down.”

Luna obligingly hopped on. Celestia settled herself gently on the opposite side, and the two began to speak.

It was awkward, and did not grow easier. Celestia started at the most coldly logical place: she asked about Nightmare Moon, and where the line between it and Luna laid.

The questions hurt. Luna fought down tears as they came, though she knew her sister was right to ask. Celestia had lived a thousand years without answers, and had a right to be suspicious. Luna could feel her sister gazing intently at her, probing for any signs of a lie.

She need not have. Luna’s eyes were firmly on the floor as she answered, yet the words rang true.

And the truth was, she could remember it all. There were years of building jealousy. A silent, seething anger, growing until every gift and praise sent to Celestia seemed a bitter insult to herself. First it was a guilty rage, of “not being good enough.” Then it was directed to the ponies. She would rant and grumble in private, decrying the ungrateful louts for their ignorance of all she did for them. And the anger kept growing, eventually turning itself to Tia for eclipsing her so.

At the peak of her adolescent spite, Luna invited dark magic to merge with her own. The deed was almost innocent, with no plan for conquest, murder, or anything so wicked. She just wanted to be the “big sister,” and shove Tia down a peg.

Luna’s face was stone as she spoke, but regret filled her every word. She owned Nightmare Moon. She was Nightmare Moon. The dark magic twisted her feelings, locking her in an endless rage. The rebellion, the hangings in Baltimare, the attack on the castle… to her maddened perception, all those were righteous vengeance against the older sister.

Her better nature tried to fight it. But the anger fed itself, growing stronger and stronger until all else fell but a burning, bitter hatred for Celestia. It filled Luna’s world, dictating the course of her every action. It was why she demanded ponies worship her like a god – to show she had grown more “beloved” than her sister. When Tia challenged her in the palace, the hate bid her break the neck and leave, giving her a chance to recover so more pain could be dealt. No room was left for thoughts of consequence, or even victory. The hate became an end itself, whipping Luna into its mad frenzy.

“You said it was dark magic?” Celestia mused neutrally, still wary. “But I used my aura to dispel any enchantments that might’ve been on you.”

“No, no,” Luna shook her head, biting hard on her lip. “It started that way. But the magic just lent me emotion. Like how when you’re angry at a pony, hitting them feels like justice. When you calm down you feel bad about it, but I could never calm down. When the dark magic fell away, I remained Nightmare Moon. Because it felt so great to cut loose, so great to be righteously angry, that…”

Luna choked on a sob, and brought a hoof to her mouth. She didn’t want to go on. She wanted to curl up and give in to the tears fighting to emerge.

But she had to say it. For Tia’s sake, she had to finish. Tia, sitting right next to her, watching stoically.

Hug me, Tia! I need you!

But the white alicorn remained still, and the space between them went unfilled. Luna’s last words came out in a babble as she raced her tears. “Tia, I wanted it! I chose to stay Nightmare Moon. It felt so good. I wanted to hurt you, and I’m so sorry! I hurt so many ponies, I hurt you, I, I…”

“Tia!” She propelled herself into Celestia’s chest. Luna wrapped her sister in a hug, bawling like a newborn. She moaned shrilly with the tears, pressing her eyes to the long white neck.

Celestia tensed at the sudden contact. Slowly, the older sister brought her forelegs around and returned the hug. Her grip was limp, like she was just setting her hooves behind Luna’s back. But Luna didn’t care. She loved it.

“It’s alright, Luna,” Celestia offered calmly. “It’s alright.”

Celestia squinted, trying to think of what else to say. “I forgive you,” was safe, but what was there to forgive? The events were scant hours past in Luna’s perception, but for Celestia, it had been a thousand years. If she ever resented Nightmare Moon, time had dulled the feeling to nothingness.

Except the Nightmare Moon who stalked her through the mirror. She hated that one with passion, but it did not count.

There was a second safe response, one that rolled more easily off her tongue. “I’m sorry, too.” Belatedly, Celestia remembered she used to nuzzle Luna at times like these. She did so, and Luna returned it.

“I played a role in this,” Celestia went on. “I should have been a better sister. I should have stopped that all from ever happening.”

A bitter twist came to her face, unseen by Luna. I should have stopped it. The mare I should be would have stopped it.

“But things will be different,” Celestia went on, gripping her sister just a bit tighter. “I promise you, Luna. Things will be better. I’ll make sure of it.”

Luna beamed, drinking in the words. Celestia held her a little longer, smiling softly as Luna snuggled closer.

Celestia finally looked to the clock and frowned. “Hm. Midnight already.”

She gently pushed Luna away, but paused to rub a hoof under the blue chin. “Welcome home, my dear sister.”

The response was enthusiastic, and wet with joyful tears. “I love you, Tia!” Luna went for another hug, but Celestia was already standing from the couch. The sun princess walked to her desk and began pushing aside cluttered papers in a brief search.

“Now where did I put that bell?” She lifted one of the trays, giving Luna a distracted smile. “I’ll summon the night servants. They’ll set you up in our finest guest room, at least until more proper quarters can be arranged.”

“But…”

It was all Luna got out before descending into meek silence. Her head and ears drooped low, and her eyes looked away.

The tone caught Celestia’s attention, and she turned back. “Yes?”

“I was…” Luna trailed off again. She looked up at Celestia with timid eyes, finally rallying her courage. “I mean, c-can I spend the night with you?”

Celestia sighed. A gentle smile quickly formed on her face, and she nodded. “Of course. Just like old times.”

Like the sunrise, Luna’s grin rose. She giggled happily, pressing her body to Celestia’s as they walked to the bedroom. She jumped onto the bed with childish cheer, twisting into the covers as Tia removed her regalia.

Celestia climbed under the sheets, glancing away as Luna snuggled up to her.

In that glance, she saw Sombra sitting on her chair.

“What a touching reunion,” he said, voice dripping with bitter sarcasm. “Come on, ‘Tia.’ We both know what you really think.”

Celestia tensed and rubbed Luna’s ears, hiding the conversation. “Go away,” she hissed softly. “You only come when I’m alone!”

“Come? Go?” In the mirror, Nightmare Moon stepped into view with that mocking smile on her face. “We’re always here, sis.”

No more words, but Celestia’s lips curled from her teeth in a brief snarl. She rolled purposefully away from them, bringing her well into Luna’s side of the bed.

Unaware of the visitors, all Luna noticed was Tia curling up closer. She didn’t mind at all.

Author's Notes:

Luna/Nightmare Moon has always posed a bit of a quandary inside the fandom, with no clear answer provided for how the corruption and redemption all went down. The common explanations behind them have never appealed to me.

A frequent portrayal is for Luna to have been possessed by an outside force, seizing a moment of weakness to hijack her body. This rings tunelessly to me, as it entirely absolves her of blame.

Why is that bad? Because without the element of redemption to her character, she becomes a lot more bland. With Nightmare Moon being all the fault of some nebulous evil, Luna has nothing to apologize for. She has no guilty conscience, no sordid past weighing her down. She becomes a flat character, with the single quirk of being out of her time.

Another theory is that she willfully became NM, but the Elements somehow blasted that part of her personality out of her. To me this smacks too much of "personality rewriting" dystopias, where deviants have their attitudes forcibly altered. This would be an odd thing to put in a children's show, and again, I feel it harms the character. If this were true, the "Luna" we see in the series is not Luna. It's a different person, with a different personality. Arguably, death would be more merciful than forcing NM to become something utterly alien to her.

Thirdly, and less used than the above, is the notion that nothing mystic at all changed NM to Luna. She was defeated, moved by Celestia's forgiveness, and turned over a new leaf. This actually kind of makes sense, and fits with what they've done for other villains. I don't so much reject it as I admit to not liking it. Plenty of accessories to genocide were totally, no-foolin' sorry when they found themselves on the losing side of a war or courtroom. And NM... kinda woulda beat them all in body count if she'd have succeeded in bringing eternal night. The notion that Luna can get away with it for being "sorry" (only when she found herself defeated) goes against many reasonable standards of justice.

So, not liking any of the common theories, the above chapter holds my own. We are not ourselves when our emotions are out of control, and it's not unreasonable to think magic can affect them. So picture a jealous Luna, who summons dark magic to grow stronger than her sister. It takes those bitter emotions and stokes them until she's blind to all else.

She is responsible. "I'm angry," is and always shall be a poor justification for violence. The dark magic does not bring any emotion that is not already there. Yet at the same time, she is somewhat absolved. The argument that a person must control their emotions becomes more difficult when they are subject to magical influence. True, Luna summoned the dark power, but she never intended there to be revolution and chaos. Looked at it this way, she is no more guilty than a child who found a gun.

Now, to the stage enters Luna. Her spite once got the better of her, leading to the mistake of a lifetime. But she's good at heart, and always has been. That goodness leads her to guilt, and a desire to do right.

And she has Tia, to help her on her way. So she believes.

(Thanks for putting up with my theory-hammering. Have a good one.)