Everything hurt still.

If Sunset was being completely honest, 'sore' was probably a better descriptor than 'hurt' but she felt that she was well within her rights to complain. A steady diet of aspirin over the last two days had only done so much, and while she had avoided any broken ribs? Her barrel still throbbed when she moved wrong.

What bothered her more was how little she knew about what had happened. In the aftermath, she and Cadance had been whisked away to the castle under heavy guard. (Stress on heavy - each of them had moved with a double-thick unicorn shield over them and an entire platoon of armored bodyguards watching every angle. Once they had gotten close to the Palace, that had been joined by a grimly stoic Princess Celestia who said nothing but looked ready to slay a dragon with her gaze.) But aside from that the four guards who had protected them were recovering from their wounds and that the perpetrators had not yet been found yet, Sunset hadn't been told anything. And the mystery was bothering her more and more with each passing hour.

So she busied herself: there were always more books to read and more knowledge to gain. Secluding herself in her room and burying her face in an ancient tome was a good way to distract herself and not think about Cadance.

Well, not really. The pink alicorn kept creeping into Sunset's thoughts. Following the assassination attempt, Cadance had been... fine. Almost too fine. Not that Sunset was unhappy about it, but she had expected Cadance would be an emotional wreck. It had been everything she had feared those months ago: her normal life interrupted by that of a princess, suddenly and violently. Six ponies had been hurt in the process - Sunset, the four guards, and one bystander who had been trampled in the panic. Cadance had been concerned, but she hadn't been distraught.

Sunset feared that Princess Celestia had been right. Or worse yet, that she had convinced Cadance of that 'ignore your emotions, stop being a pony' idiocy. Forget how that would interfere with Sunset's own plans, the damage it would do to Cadance as a pony was unthinkable. When they saw each other next, Sunset was going to have to make sure Celestia hadn't done something stupid.

Her thoughts were broken by a knock at the door - heavy and rushed.

"Yes?"

The door swung open.

Cadance stood there. She was distraught. She was an emotional wreck. Her eyes were red, cheeks matted with tears.

A tiny bit of Sunset breathed a sigh of relief. The rest stood in shocked surprise. Book forgotten, she rose to her hooves.

"I need you." Cadance surged into the room and into Sunset's embrace. "Please."

There was no hesitation for Sunset to hug her tightly. "What happened? Who--"

Cadance shook her head, eyes pinched tightly shut. She couldn't find the words, huffing quietly as she held on tight.

A part of Sunset demanded answers as it always did - but she realized this wasn't the time. So her magic closed the door while her body half walked, half carried Cadance over to the bed.

The light was snuffed out, leaving them to lay together in a tight embrace until morning.

Cadance only released Sunset after several requests and one threat that she really had to pee. Once the embrace was broken, they were able to find at least a little normalcy in the morning - Sunset returned with a plate of danishes and a carafe of coffee. She found Cadance standing at the window, the heavy blackout curtains pulled aside and letting in the sun.

Sunset quickly pulled the curtains closed again with her magic. "Breakfast," she declared.

They sat together at the little table and shared out the plate. But Sunset held the coffee just out of reach. "Are you going to tell me what happened?"

Cadance's lips pursed. "I... after?"

"Promise?"

"Promise."

And she was allowed her coffee.

Breakfast was largely silent. The sound of chewing and sipping thunderously echoed in the little room, overrunning their breathing. When only one danish remained, Sunset Shimmer tried again. "So. Who did what? Because with Blueblood gone I've got some room to extract revenge."

Cadance's utterly horrified look smothered that joke and killed the conversation for another few minutes.

But she eventually did speak. "Princess Celestia and I had a talk," Cadance began. And paused briefly there to give Sunset a sharp look, squashing any ill-advised assumptions on the unicorn's part. "She told me..." A long, steadying breath. "She told me a story. It's an important one and it shook me. It... it explains so much about everything."

"What story?" Sunset jumped in, having the sense to ask a relevant question rather than launching an attack at the Princess.

Cadance shook her head. "No. I won't-- I can't tell you. It isn't my story to tell. I don't have the right to. You have to talk to her about it." She paused for a moment. "And she should talk to you about it." Something turned in her head, setting Cadance's face to stony seriousness. "I think she has to."

Lost on a lot of the context, Sunset could only shift uneasily. "Okay?"

"I'm sorry Sunny." Cadance sighed, drooping. "It's going to make more sense after you talk with Princess Celestia. It's something she's been hiding for a long time and it's hurting her. She told me and I think if she tells you it could help ease her pain."

Sunset pursed her lips. "And it's something I want to know?"

Hesitation. "Maybe," Cadance settled on. "But I think it's important that you know, for both of your sakes." She reached out, hugging Sunset. "Please trust me?"

Sunset hugged Cadance back. "Alright. I trust you."

She could feel Cadance smile against her cheek. "I'll tell the Princess. When you're ready, meet her in private and ask her about the Nightmare."

It was a rare occasion for Sunset to be allowed into Princess Celestia's room.

The Princess had layers to her privacy: there was the Palace itself, which closed out most of the world; the private areas of the grounds, which didn't allow the public tours to enter; the residential wing that sat separate from the sections of the castle that served governmental functions; the Princess' apartments that included her various meeting, sitting, and dining rooms; and finally Princess Celestia's bedroom itself. Including the staff who came around to clean and change sheets, there were perhaps a dozen ponies alive who had ever been inside. Sunset was one of them, but it was infrequent enough that she had more teeth than visits.

Given how secretive and upsetting Cadance had said this topic was, however, it was a place that made sense.

Sunset arrived shortly after moonrise, entering the Princess' room alone. The guards had left her at the door - past there, she was on her own. Celestia's room was just like Sunset remembered: pastel purple with gold highlights all around, a great canopy bed with a gilded sun in the headboard, and thick aqua carpet underhoof. Celestia herself was there at her balcony, watching out at the just risen moon. Sunset approached, stopping in the middle of the room and waiting for the Princess to begin.

"Sunset Shimmer."

"Princess Celestia."

Silence lapsed again.

Sunset took a step forward. "Cadance said I should ask you about a nightmare you had." She tried to chuckle, but it felt fake. "It must have been pretty bad."

Princess Celestia didn't turn around. "Not a nightmare. The Nightmare."

It took a moment for Sunset to realize there were capital letters there. "Wait, like Nightmare Moon? The fairy tale monster from Nightmare Night?"

"She--" Celestia started to speak but found the words... simply didn't come. "What I am going to tell you, Sunset Shimmer, is of the utmost secrecy. You will be only the third living pony to know of it and there cannot be a fourth. Do you understand?"

There was something in the Princess' voice that chilled Sunset. It took her a moment to realize: this was a threat. Over the years, Princess Celestia had said many things to Sunset. She had advised; she had bribed; she had pleaded; she had demanded. She had never threatened. Not until now.

Sunset swallowed roughly. "I understand. I will never speak of this to another pony aside from Cadance and you."

Celestia nodded her head slowly, still looking out towards the night sky. "Nightmare Moon is real." The words were tough to say, sticking to Celestia's throat like glue. "I called her sister, once, and we ruled side by side."

Sunset Shimmer said nothing. She couldn't. She was entirely frozen, both body and mind. Another pony had ruled Equestria at Princess Celestia's side. A pony who foals laughed at while sacrificing candy to her. It made no sense. There were no records, no tales, nothing--

"Equestria was newly formed and we were brought to take the throne." Celestia twitched. "Thrones," she corrected.

Thrones, plural. Sunset's world (and body) shook as words spilled out of Celestia.

"We were a compromise. None of the pony tribes felt they could trust us, but they trusted each other even less. Crowning a ruler of any one tribe would smother Equestria in its crib but an outsider might be acceptable enough. We gave the illusion of impartiality." A low chuckle slipped from the alicorn. "That's why 'princess', by the way. Each tribe thought they would eventually place a queen over us, once everything stabilized." She shook her head. "But that never happened. We proved ourselves both more wily and longer-lived than the tribes had expected. In time, those treacherous designs were forgotten and we ruled for more than a century. I with my Sun and she with her Moon."

The Moon. It all started snapping into place. The reaction to Cadance's moon-shaped medallion gift at Hearth's Warming. Celestia's sorrow when she insisted that Cadance needed to be protected. The cold intensity of the moon being raised that left Celestia gasping and winded. Her talk of isolation and the weight of centuries.

"But that was before we..." Celestia stopped, throat dry. "We fought," she croaked.

That snapped Sunset out of her daze. "Fought?"

Celestia slowly nodded, eyes tightly shut. "Yes."

"...How?"

One of Celestia's eyes cracked open, staring at Sunset with amused confusion. "How?"

"How," repeated the student. "How could anypony stand a chance against you?" The subject was leading - but Sunset's question was more out of sheer disbelief than cunning.

A low, quiet laugh slipped out of the Princess, bitter like cranberry. "I was much younger then. But she..." Another hesitation. "She found power. She had always been my equal, but that night she called on something terrible. It's what made her the Nightmare." A shudder passed down the great alicorn's spine. "It's what allowed her to defeat me."

For the second time in as many minutes, Sunset's world fell apart. Princess Celestia had been defeated. There was a power out there that was greater than the Princess.

Unheeding of Sunset Shimmer's mind being blown, Celestia rambled on. "It was only with the power of the Elements of Harmony that I was able to stop her."

That managed to pull Sunset out of it, at least a little. "Elements of Harmony?"

"Ancient artifacts of great power," Celestia sighed.

Sunset's heart skipped a beat.

"Unfortunately, my abuse in banishing Nightmare Moon led to them losing their power."

The brief burst of elation in Sunset's heart faded. But she was out of her shock now and took a step closer for the first time since the conversation began. "So she ruled with you, then you fought." The Princess nodded. "Why?"

And that was either the best or worst question as it made Celestia's entire body slump. Silence. Silence for far too long. Then, with a meekness Sunset had never heard from the Princess before: "It was my fault."

"What?"

"It was my fault," Celestia said with greater strength. "I drove her to it." Finally turning away from the Moon, she crossed the room to a dresser of gilded ivory. Opening a middle drawer, she pushed aside a variety of grooming accessories - hoof trimmers and featherbrushes and crown polish - to extract a plain-looking wooden box that had been shoved in the back like a filly hiding her diary. The box opened and the raw power of all the preservation enchantments made Sunset's horn ache. "Most of what remains from her is locked away either in the deepest of storage or in the secure vaults, but I've kept a few mementos to remind me of what I did." Golden magic pulled out a few seemingly random odds and ends from the box.

A small gray rock, roughly carved into the shape of a frog. Two Hearth's Warming dolls - one very familiar to Sunset, the other made by the same hoof but of a navy blue alicorn. A long-stemmed rose made of carefully shaped metal. There were perhaps a dozen such trinkets in there, each practically throbbing with layer upon layer of magical wards to keep them intact.

"I keep these," Princess Celestia stated with reverence and shame, "As a reminder of what I destroyed. Occasionally I pull them out so I don't forget what my hubris caused."

Sunset inched closer, eyes squinting slightly as she looked the frankly childish items over. "I don't understand."

Golden magic lifted up the rose, slowly turning it in the air before the Princess' eyes. "She wanted to be given her due. Loved by ponies the way I was and to be an equal at my side. For night to be as loved as the day was." Her magic flickered for a moment, like a candle's flame when the door is opened. "I was so caught up in my own ego that I didn't see her pain."

It was in that moment that Sunset understood. This was something that had shaken Princess Celestia to her core. She had carried this harsh lesson for a thousand years - and she hadn't learned a thing.

"Her rebellion was a cry for help." Celestia's eyes didn't leave the flower. "One I should have heard years before. But I didn't. I reveled in the privilege of the Crown, too busy with my own foolishness, and so I let the wound fester until it destroyed her."

Sunset Shimmer shifted uneasily. Every bit of her felt the need to throw a barb about how Celestia was repeating the mistake with how she treated Sunset - but every bit of her also demanded she stay silent because that was liable to make the Princess mad mad.

Finally, Celestia set the flower aside, leaving it atop the dresser with the other items. "That is when I finally understood the meaning of Duty, Sunset Shimmer. We spoke about how to be a princess is to stop being a pony and this is why." She turned away from the mementos, finally facing Sunset for the first time since the conversation began. "One day Cadance will face the choice between her desires and the good of Equestria, just as I did."

Hesitantly, Sunset took another step closer and injected herself into the monologue. "And you chose Equestria."

"And there is not a single night I do not regret it," said Celestia gravely. "But it also would not have happened in the first place had I not given in to my own weakness and ignored her. I became enamored with my own foolish desires until the cost of my negligence demanded to be paid. And it cost me her."

Another step closer. "That doesn't make sense," Sunset ventured. "You're mad that you didn't care for her enough, so your solution's to close it all off?"

Celestia shook her head and turned away from the filly, once more looking to her keepsakes as they lay there. "You do not understand." She sighed, shoulders sagging under centuries of weight. "And no, it isn't because you aren't smart enough or aren't ready. You simply haven't experienced things that would allow you to understand - and I am thankful you have not." She paused - then laughed bitterly to herself. "I'm not sure why I'm even telling you any of this, my brilliant student."

"What?" The sudden shift - Celestia moving from sharing more than she ever had before to closing off again - set Sunset's brain spinning.

The wry amusement clung to Celestia's face and voice. "The teacher's duty is to elevate the student, not burden her. You shouldn't have to suffer for my sins, Sunset. No more than you already are." That familiar soft smile came to Celestia's lips as her tone turned motherly. "Cadance has no choice, but you might yet live a normal life. You should not be cursed with the knowledge and duties that consume us."

And instinctively, Sunset dug in. "Normal life?! What do you expect me to do, give up everything I've built so I can become a farmer? No, wait, a baker? Is that what you think? I'll throw away everything I am so I can go make cupcakes like a good little pony in some Canterlot alleyway?"

"Preferably a different city," Celestia suggested with tongue slightly in cheek.

Sunset didn't find it as funny. "That's even worse!"

With a heavy sigh, Celestia paced to her bed. Her massive form laid down, the impossibly plush cushions crushing under her weight. "It is my hope that once you graduate from my tutelage, you will go far away from here. You will find some measure of fame and happiness in a place that is safe. Because you deserve it, my brilliant student."

Fury - blind, boiling fury - overwhelmed Sunset's mind and turned her vision red.

And yet Celestia continued. "Perhaps I should send Cadance with you once you move on. She keeps speaking about how she wants to return to that normalcy. It might ease her mind for a few decades." Her eyes flicked to Sunset's fuming face, something deep in her ancient eyes bordering on a plea. "And then you will not, as you say, give up everything."

Sunset didn't notice the look. "How dare you," she seethed. "Cadance comes to me in tears, devastated by what you told her. I came here to find out more and you casually overturn all of Equestrian history. Then you stop halfway through to announce I'm not worth telling the story to!"

Celestia's face fell. "Sunset, that's not what I--"

"No!" Blood boiling, Sunset stomped her hooves, the carpet muffling it and ruining the dramatic effect. "No more! I'm tired of you treating me like some-- Like a plant in your garden!" Celestia's grimace told that she had heard the comparison before. "A thousand years and all I'm hearing is that you keep hurting the ponies you claim are important." A brutal sneer crawled across Sunset's lips. "Cadance cares about you because she cares about everypony, but past her? It's pretty easy to be above it all when you've driven everypony else away."

Irritation rippled through Celestia's face, surfacing for just a moment before she suppressed it again. "Sunset Shimmer, you cannot speak to me that--"

"I can and did," cut in the unicorn. Ever defiant, she tried to turn her nose up at the much taller Princess. "And I'm leaving. Cadance said it was important I know what was going on. Now I know and since you obviously don't think I'm worth telling more, I'm going to get on with my blissfully ignorant life." She turned, heading towards the door.

Celestia stood, rising off her bed. "Sunset Shimmer, I forbid you from leaving until I'm through talking to you."

Sunset stopped at the door and glanced back. "You can't stop me."

She could.

They both knew it.

She still didn't.

And that was how the last conversation between teacher and student ended.

Author's Note

I had to rewrite this chapter twice because I accidentally redeemed Sunset Shimmer several years too early.