The sun poked above the horizon on the outskirts of Canterlot. Beneath the cloudless sky, Spike busied himself digging a wide, shallow hole. Several massive wooden crates held large crystal spires, awaiting their proper placement. Another box held a collection of not-yet-floating gems. Next to the hole in progress was a massive crystal slab, rounded underneath. Some wood repurposed from its packaging held it steady as Twilight Sparkle walked on top of it.
She slowly walked around the top of her slab, horn lowered. A stream of magic emitted from it slowly carved a fresh magic circle in the crystal. Twilight's eyes darted back and forth between her carving and the scroll hovering next to her.
She stopped to double-check her work.
"Twilight Sparkle."
She looked up to see a white figure approaching. "Princess Celestia! I—"
"What is the meaning of this foolishness?" Celestia's eyes were thin and her jaw set.
Twilight hesitated. "I found a way to recreate the Nexus, Princess Celestia. I'm going back to the past."
Princess Celestia walked to the edge of the slab that Twilight was standing on. "Did I not say that you did not return to the past? Did I not say that it was impossible? That this is all an exercise in futility?"
Twilight walked to the edge, her platform letting her look down on her Princess. "But... I double- and triple-checked everything. All the magic works out. Every contingency has been eliminated or accounted for. I've even made some minor improvements on the design. There's no way it can fail!"
Princess Celestia turned away. "You are going to send these components back to where you got them. You will return to Canterlot and you will cease these childish flights of fancy. I will not hear any further discussion on this topic."
Twilight sat, open-mouthed, as Princess Celestia walked away. The Princess flew into the sky, leaving her Magician in shock for several minutes.
"Twilight?" Spike asked, leaning on his shovel.
Twilight shook herself back to reality. "Spike..." She looked at the crates containing the pieces of the new temporal apparatus. Twilight closed her eyes. Faces burned into her memory crossed her mind's eye. She mentally replayed their smiles, their laughter, the sounds of their voices.
"Keep digging, Spike."
---
That evening the sun set on a pony and a dragon in the backyard of their house. The yard was filled with magic lines and circles. Large glowing gems had been carefully arranged to properly focus the magical power. At the center, a brilliant purple light shone from the impromptu magic forge.
The light of creation dimmed, and Twilight Sparkle walked to the center. Careful not to cast any stray spells in the heart of the forge, she picked up a piece of craftsmareship and took it out. She then brought a new piece of carefully ground amethyst crystal to the center, placing it in its stone stand. The High Magician exited the circle and lit her horn, activating the forge and producing the brilliant light once more.
A minute later, the next piece was complete. Twilight removed it from the forge. She looked over her inventory of twisted and compressed gems. "Spike," she said, "help me configure the forge to final assembly mode."
Spike nodded. The two moved focuser gems and redrew circles without saying a word. Once done, Twilight took the pieces that had been made and set them in the center, arranging them carefully to the pattern she had worked out.
"It doesn't look like much," Twilight said, pointing to the mishmash of gems and metal, "but it'll become Sweetie's and my ticket back."
Twilight started her spell, then stopped. "Spike... before I forget. Thank you for helping me out with this."
Spike smiled. "I wouldn't be your number one assistant if I didn't!"
Twilight shook her head. "No no, I mean, I'm going to leave you again. This time it'll be forever."
"Which is why I'm spending the time I have left with you doing what makes you happy, Twilight." Spike wiped away a tear. "I'm not going to keep you away from the ponies you care about."
Twilight smiled back. "Thank you Spike. It means a whole lot to me."
She cast her spell. The forge lit up brighter than ever. Magic coursed along the lines and through the foci as Twilight Sparkle's greatest invention came into being.
---
One slab sat buried in the earth. Six crystal pillars rose above, the midday sun casting short shadows. A plethora of magic lines surrounded them. Spike arranged dozens of loose gems around the base.
The temporal apparatus was again complete.
Twilight paced around the device, double-checking the components' places. When she next looked up, she saw her daughter approach, a lightly-burdened saddlebag slung over her side.
"Sweetie Belle," she said, "we really shouldn't take anything with us when we go back."
"It's all right, Mom." Sweetie looked at her bag. "I think this is important enough to go."
"I don't think—"
"Twilight Sparkle!" The voice boomed across the landscape. "I thought I told you not to pursue this foolish notion!"
Twilight, Sweetie, and Spike turned to see Princess Celestia land.
"Princess, look!" Twilight held up her creation. It was not the Nexus of Starswirl the Bearded. The object that she held was still shaped like a book, with a white cover, rimmed with gold. Unlike its long-destroyed predecessor, this Nexus had pages of amethyst instead of topaz. It had been crafted by the greatest unicorn to ever walk Equestria, who now held it: the Nexus of Twilight Sparkle.
"See? I did it! I'm going back!"
Twilight set her Nexus on the stand in the center of the apparatus. Light pooled out through the slab, across the magic lines, and up the pillars. The loose gems rose into the air and slowly began to orbit.
"It works. It works! Princess Celestia, it works!" She began to hop in place. "I'm going back!"
Princess Celestia stomped the ground, putting an immediate end to Twilight's celebration. "You are not going back, Twilight. You did not return. Do you understand me? There is no way back to your time."
"Princess Celestia."
Twilight had opened her mouth to reply, but it was not her voice that answered. She turned to look at the new arrival.
"Princess Luna? What are you doing here?" Twilight asked.
"I am here to see you off, Twilight. Celestia, don't you see? She has attained what she has sought. You failed, Celestia."
Twilight interrupted. "What do you mean, failed? And how did you know I had rebuilt the apparatus? Did Princess Celestia tell you?"
Luna turned to Twilight. "It was simple, Twilight. When you returned to your time, I noted the time that you were away. When you reappeared here, it was trivial to calculate the date of your departure."
"Luna," Princess Celestia said. "You have gone too far!"
Luna grit her teeth. "No, Celestia. Your planning has failed you. Twilight Sparkle will return to the past, just as causality dictates."
Twilight looked down, eyes darting around the ground. "My return? So... I did come back? But then... how could..." She trailed off in thought.
"Twilight Sparkle." Celestia kept her authoritarian tone. "I forbid you from using that apparatus! You will remain in this time. Do I make myself clear?"
"Celestia." Luna softened her voice. "You cannot change the past, sister. It is over."
"No." Celestia's eyes moistened. "It is not over. I am not changing the past; I am changing the future."
Twilight looked between the princesses. "Did I go back or not?" She then looked to the dragon. "Spike? You can tell me, right? Did I come back?"
Spike looked down. "Princess Celestia told me... she used a bunch of big words I didn't understand. Said that if I said you came back it would break time or something. I wanted to tell you, Twilight. That you'd see your friends again. Honest."
"But then..." Twilight looked around, bewildered. "How can Princess Celestia think that I didn't?"
"Indeed," Luna added, smirking at Celestia. "Do tell, sister. I rather distinctly recall you spending an inordinate amount of time with her after her return."
Celestia did not answer.
Twilight thought hard. "Then... the only explanation could be..." Her eyes went wide. "You lied?"
Princess Celestia avoided eye contact. "I'm sorry, Twilight."
"How could you lie to me, Princess?! I trusted you! You... you convinced me to give up on going back! You kept me here for a decade! Away from my friends! If I hadn't seen that painting, then I might never have found the way back!"
"A painting?" Princess Luna raised an eyebrow. "It seems you missed something, dear sister."
"But why, Princess Celestia? Why? You taught me about friendship, how important it was to have friends, and then you took them away from me! How could you do this to me, Princess? I need to know! Why?"
Princess Celestia continued to look down. "Because Twilight... you died."
Twilight took a step back. "D-died? I died? How? When?"
Luna stepped in. "Knowing the time or manner of your death will only serve to drive you mad, Twilight. Suffice it to say, you are mortal and will not see this era again."
"But Princess Luna, why didn't you tell me that I went back? Maybe I could have gone back sooner if I'd known about the painting."
"It would not have affected anything. You were fated to leave today, not five years ago. I would only have granted you anxiety. And you never told us how exactly you created your Nexus." She looked sidelong at Celestia. "I am fairly certain as to why."
"And... I didn't see anything in the magical journals about me. Didn't I do anything noteworthy for the rest of my life?"
"A result of some rather creative, yet thorough, editing from my sister." Luna glanced at Celestia again.
Twilight's eyes widened. "You had me erased from history? What, did I actually invent this?" She removed her amulet and threw it to the ground, the wings vanishing off of her back. "The magic lights? The transporter? Am I the first unicorn on the moon?"
"Do not worry, Twilight. The original texts are retained in my personal library, and I have taken great care to preserve them. I will personally see to their duplication and redistribution. You have my word."
"But... Princess Celestia said I died. Everypony dies someday. Surely she's lost others before me. Why me?"
"Twilight." Princess Celestia spoke softly. "You have always been special to me. I had always prepared myself for the day you'd leave me. But when you left, all that time ago, I did not know whether you had lived or died, whether I'd see you again. I spent ten years in uncertainty, not knowing if I'd ever see you again. When you returned, I felt relief like I never have before. Then, as time went on, you grew old, then left me again. I have lost you twice, Twilight Sparkle. I do not wish to lose you a third time. Please, Twilight, do not leave me."
Twilight took a breath. "So that's it? This was all for your own benefit? Ten years without my friends? The friends that you insisted I make?"
"Twilight, please—"
Twilight stomped the ground. "No, Princess Celestia. I am not bowing to your whims just because you want to keep me on a leash. I am leaving!" She turned away.
Celestia hesitated. "Twilight." She looked at her Magician.
"What?" Twilight whirled around.
Celestia looked away again. "When you return, and see me again, please do not hate me. My past self did not have this scheme against you. I have many happy memories of us together. Please do not taint them with the knowledge that you had anger in your heart. And Twilight, please forgive me."
"I don't know if I can, Princess." Twilight looked at Celestia with narrowed eyes.
"Twilight Sparkle, I beg you." Celestia looked into her eyes. "I cannot stand the rest of eternity not knowing whether you forgive me."
"I... I can't decide. Not now." She thought a moment. "Princess Luna. I'll go back, and have the rest of my life to decide. When I do, I can tell you, and after I leave, you can tell her. Does that sound good? Did that happen?"
Luna said nothing, but nodded.
"There. See? Everything's taken care of." Twilight closed her eyes, took a breath, and exhaled.
She put on a smile. "It's been swell seeing the future, but it's time for me to go. I figure I can take the apparatus back to the moment I left and at least save my friends the trouble."
Luna spoke up. "It did not happen that way, Twilight. You were gone for ten years."
"What? But this is my Nexus, and my apparatus. There's causality, and there's silliness. Why can't I just tell it to go whenever I want?"
"Accuracy, Twilight. It has been a long time, but I recall you aiming for an initial jump of approximately two hundred years. With an error as large as it was, can you guarantee that you will even arrive within your friends' lifetimes on your next trip? Can you afford another breakdown, one that may damage something less replaceable than Nexuses and crystals?"
Twilight opened her mouth. "I... don't know." She closed her eyes to think. "I need... some way to target the right time." She could feel her heartbeat in her ears. Twilight opened her eyes. "I know. My heart, and theirs. The time jump brought them out of sync, so all I have to do is aim for synchronization, and I will arrive with them... but with the same passage of time. Oh Princess Luna, I'll have left them for ten years, too?"
"I am sorry, Twilight."
Twilight sat down, fixing her eyes on the gems swirling in the apparatus. She imagined her friends spending the years without her that she spent without them. Images of shouting and crying ponies filled her head. She imagined seeing their parents as young foals, or their children as elders.
Twilight sighed. "I can't think of any other way. I guess this is goodbye, Princess."
Luna nodded. "You will see me again in the past, Twilight, but for me this is farewell. I remember you well. You will become a great pony, and the world will remember you for a long time, once I set things right."
Twilight looked to Celestia, then snorted. "I'll see what I can do about you in the past, Princess. Ask Princess Luna once I'm gone."
Celestia choked up. "Farewell, Twilight Sparkle, and please forgive an old, foolish mare's selfish desires."
"Sweetie Belle?" Twilight looked for her daughter.
Sweetie Belle sat off to the side next to Spike. She rolled up a scroll she had been writing on and placed it in her bag.
"Sweetie Belle?" Twilight repeated, getting her attention. "Have you said your goodbyes?"
The mare walked up to her mother. "Not yet." She squeezed her eyes shut, then jumped forwards into an embrace. "Goodbye, Mom!"
Twilight pulled her off. "Sweetie Belle?"
Sweetie Belle stood, looking into her mother's eyes. "I'm not going back. I'm staying in this time."
"What do you mean? Why aren't you going back? Princess Luna." Twilight turned to her. "Sweetie Belle came back too, right?"
Luna replied, "I will not influence her decision."
"I can't go, Mom." Sweetie Belle put her hoof over her heart. "You belong in your time, and I belong in this one. I have my friends here, and my career, and the troupe. And I have Spike. We've talked, and he's going to live with me from now on. So we can take care of each other."
"But," Twilight started, "what about Apple Bloom? Or Scootaloo? Aren't they your friends, too? What about Rarity? Don't you want to see Rarity again?"
Sweetie Belle blinked back tears. "I do want to see her again... and I miss her. But if I go, I'll miss Apple Crisp and Spot Light and the rest of the troupe. I made my decision, Mom, which is why I brought this." She levitated her saddlebag off of her back and onto Twilight's. "Give this to them when you get back."
"Sweetie Belle!" Twilight swept her into a hug, tears running down her face. "I don't want to leave you behind! You mean so much to me!"
Sweetie Belle nudged Twilight backwards. "I know, Mom. But I have to stay behind. I'll look up as much as I can about you. And I'll have plays written about you. And I'll sing about you on stage in every corner of Equestria, so the whole world knows how great of a pony you were! And I'll plant trees! Lots of trees! All over! I'll show them what it means to sit under a tree in the summer, or have an apple right off the branches! And maybe, one day, medicine will let me fly. And when I do, I'll make as many clouds as I can. I'll make beautiful patterns in the sky, and encourage everypony else to make some too! I'll make Equestria somewhere you can be proud of, Mom!"
"I love you, Sweetie Belle!"
"I love you too, Mom! Thank you! Thank you for everything you've done for me!"
When they released, Twilight found herself standing at the center of the apparatus. "Sweetie Belle... I'll miss you. I love you, so so much, Sweetie Belle."
"I love you too, Mom." Sweetie fought back tears as she backed up off of the slab.
"Spike?" Twilight looked at the dragon. "There's room for one more. Do you want to come back with me?"
Spike shook his head. "I'm already in the past, Twilight, happy at finally seeing you again. There doesn't have to be two of me. Besides, Sweetie Belle needs someone to keep her out of trouble with you gone."
Twilight sniffled. "I don't know if I'll ever say it in the past, so... I do love you, Spike. And I appreciate everything you've ever done for me."
"I know, Twilight. Say hi to past Spike for me. And... I love you too. Now don't keep your friends waiting any longer."
Twilight looked between the two Princesses, to her daughter, and to the dragon.
"Goodbye, all of you. I'll make sure to give you plenty of happy memories."
Twilight's horn illuminated, and the temporal apparatus powered up. Then, she was gone.