Twilight hit the cutie map and rolled off to land on the ground with a thump. She had lost count of how many times it had happened now. For a pony who counted everything, that just went to show how off the rails things had gone.
From the other side of the table, Spike snarked, “Well, that didn’t work.” ‘Again’ went unspoken.
Twilight covered her head with her hooves and groaned. This was getting ridiculous. All Starlight had to do was interact at all with Rainbow or Fluttershy or the little bullies and the timeline fell apart. Meanwhile, she had to prevent Starlight from doing the same, while not doing anything flashy enough to prevent the bullying or distract Rainbow from the race or… seemingly a million other things. The invisibility she had tried last time had seemed the perfect solution to that. Starlight had somehow seen right through it though, and yet again frozen her in crystal until it was too late.
“Hey, Twilight?” Spike called, still lying on the floor. “How come this time travel doesn’t work like in ‘Wyld Stallyns’ Excellent Adventures’? You know, the way they could take as long as they want to go back and change something earlier to help them with whatever they’re doing at the moment, as long as they planned to do it in the future,” he babbled. “When we go back, there aren’t even any past Twilights or Spikes or Starlights from the other times we went back.”
Staring up at the ceiling from where she was also still lying on the floor, Twilight prepared to deliver a lecture on the temporal mechanics presumably involved in the spell (and the proper tense to discuss something that somepony will be going to have caused to have already always happened), only to cut herself short. “Spike, you’re a genius! We actually can take our time to plan our next move instead of running straight back again!”
Looking around at where they had ended up this time, the cutie map was back inside a crystal room. It didn’t look quite right, but at least it didn’t look threatening either. With no obvious dangers looming it should actually be possible to sit down and think of a decent plan before returning. They’d still arrive at the same moment no matter when she used the spell. Actually, make that prepare several decent plans. There was no guarantee she’d easily find another world she wouldn’t be forced to run from if the first plan failed.
After offering the universe a straight line like that, Twilight glanced worriedly at the door to the room, half-expecting an evil version of Trixie or somepony to come barging in. The door stayed shut though, and with a sigh of relief, Twilight continued to ponder the situation out loud so that Spike could act as a sounding board. “Since there aren’t any previous versions of us or her, nothing we do on one trip will have any effect on subsequent trips,” she mused, “provided she doesn’t actually kill us or otherwise prevent us from trying again.”
“Hey, Twilight.”
“And since her chosen revenge requires me to be aware that she’s broken my friendships because of cutie marks rather than just killing me, that means I can just keep trying as long as I want, so I’m bound to win eventually.” Twilight smiled and nodded to herself at that thought. “As soon as we make it back from one trip where she doesn’t affect the past, I destroy the spell.”
“Twilight.”
“Continuing that thought only for the sake of completeness, if Starlight died on one trip, she wouldn’t be there on the following trip, allowing that trip to go perfectly. Of course, killing her would probably be harder than just stopping her, unless I just utterly ignore collateral damage on the basis that it won’t have happened when I go back the following time.” Which would probably mean killing a lot of foals, including Rainbow and Fluttershy. Even for something that would ‘never have happened’, Twilight suspected she didn’t have the stomach for that, and that was even if she could somehow bring herself to attempt to kill Starlight herself.
“Twilight!” Spike yelled, unnecessarily loudly.
“What, Spike?” Twilight asked, sitting up at last.
“Look at the map. Does it look a bit less… evil than the ones we’ve seen so far?”
Moving closer, Twilight could see that, yes, the map looked a lot closer to the cool blue it had been originally than the angry reds and sickly greens of the bad timelines they’d been to before.
“Huh. I wonder what that means.”
This time the universe didn’t miss the straight line, and the door banged open. Sunset Shimmer breezed in, escorted by two crystal pony guards. Twilight barely had a second to conclude that this was going to be the timeline where Sunset had overthrown Celestia or something, before Sunset stopped and shot a relieved smile at her.
“Just Twilight. False alarm guys, but good work. You were right to come get me.” The guards saluted and returned to their posts outside the door, and Sunset closed the door behind them.
“Twilight,” she said patiently, “you can’t keep teleporting in here. You’re eventually going to give the guards outside a case of ‘The filly who cried wolf’, and if somepony ever does sneak past the wards they’ll just assume one of the Element Bearers just teleported in again and not report it.”
Between trying not to panic at her sudden appearance and information overload at all the things that were implied by Sunset’s words (not least, wards to keep everypony but her friends from getting into this room! First thing she was doing once this was over!), Twilight didn’t quite manage to reply to that before Sunset’s gaze swept the room.
“Hey, is that a dragon?” asked Sunset curiously. As she turned back to Twilight, she only became more surprised. “And, woah! Twilight, you’re an alicorn! When did that happen? Congratulations! How did that happen?”
“Yes, that’s Spike. And yes, I’m an alicorn,” Twilight answered almost automatically, before her mind seized up on the when and how questions, which had rather complicated answers from when she was standing.
Sunset was staring at her intently now. “You’re taller than you should be too, and you look a mess.” Twilight had the sudden premonition that she was about to be mistaken for a changeling again, but Sunset jumped to a different (and, amazingly, almost correct) conclusion. “You’re from the future! Is there some sort of epic pony war in the distant future or something?”
“It’s… more complicated than that,” Twilight answered, somewhat lamely.
“Well, I think I can spare the time to listen to the whole story of anything important enough that you travelled through time for it.” Sunset replied flippantly, as she settled into one of the thrones around the map.
Twilight settled into another throne more slowly, with Spike doing the smart thing and joining her in case they needed to make a rapid exit. Twilight wrapped her forehooves around Spike as she thought. Was telling this story to Sunset a good idea? Even if this seemed to be a more decent alternate world than she had seen before, wouldn’t Sunset want to stop her from changing her world? Of course, that brought up the morality of doing it at all, if Sunset’s world wasn’t overrun by Sombra or changelings or Discord or endless night or Tirek or more ridiculous disasters. Were the ponies who lived here any more expendable than the ones at home? Surely not, but obviously she couldn’t abandon the ponies at home either. What to do, then?
If she was going to not tell Sunset though, she’d pretty much have to either cast the spell right now and escape or else start lying through her teeth. Throwing caution to the winds, Twilight began, “Actually, I think I’m from a different timeline rather than the future.”
Sunset listened to the whole explanation and its relevant context without interruption, though with a growing expression of worry and numerous glances at the spell laid out on the map in front of Twilight’s throne. By the time Twilight had finished everything up to landing in this world, she looked distraught and remained silent for a few moments, considering.
“If all that’s true, why haven’t you tried again already?” asked Sunset, in the manner of one who very much wished that “all of that” wasn’t true.
“I’d just realised that I could take time to come up with a plan instead of rushing straight back, since I’ll arrive back at the same time anyway. And then we noticed your map didn’t look…” Twilight trailed off.
“Like Tartarus come to Equestria?” Sunset finished for her, which was a pretty decent summary of some of the worlds they’d seen. Twilight nodded, and Sunset continued hesitantly, “Look, you must know how that sounds to me. You want to go back and try to stop Starlight again, right?”
Twilight grimaced, but nodded again. When put like that, she must sound like the bad guy from this world’s perspective.
Sunset threw both forelegs up in the air in exasperation. “And yet here you are telling me about it! As far as I’m concerned, there’s two possibilities here if you cast that spell. If what you’re doing is changing the worldline you’re in, you’ll just vanish from this world and appear in a new one, but if what you’re doing is repeatedly changing the past of one timeline, it’s the end of my world!”
“Uh… changing worldlines?” Twilight asked, wishing she’d looked up more of what Star Swirl had written about time travel after the last time.
“Well… even Star Swirl never really understood everything about time travel, did he? And there were a few ways he thought it might be expected to work. One of those was that there were all these world lines running side by side. Every time a choice is made in one of those world lines, the world line splits so that every possible choice happens in one world line or another. If you travelled back in time in that interpretation and changed something, you would end up in a different world line, but your original timeline would still be intact.”
Sunset paused to make sure Twilight wasn’t going to question that explanation, then asked, “You said you only got sucked into the past after picking up Starlight’s spell, right?” After an answering affirmative, she continued, “That sounds more like your timeline still existed after Starlight went back, and that the spell then removed you from that worldline than that she changed the timeline of that world when she travelled back.”
Twilight hadn’t really had time to spare for thinking about that since it happened, but with it drawn to her attention she could certainly see Sunset’s point. Zecora had seemed to know there was something wrong with the timeline though, which contradicted that.
“Of course, I’m not willing to bet my world on guesswork, but since I can’t imagine you’ll be willing to let me examine the spell or let me call anypony else in to join the conversation without using the spell to escape, where exactly does that leave us?”
Twilight had to stop to consider that. Sunset had made no move for the spell, but she had just heard how Twilight had cast it while under fire from Nightmare Moon. Forcing a confrontation while Twilight held the scroll might just make Twilight end Sunset’s world (if that did turn out to be how it worked), while if Sunset had the scroll in front of her to examine it, not destroying it could be argued to be simply irresponsible of her. Trusting her with the scroll, then, was an obviously bad idea. Bringing in more ponies to the discussion seemed a similarly bad idea.
“You’re right,” Twilight said apologetically, “I’m afraid I can’t show you the spell, and I’d like to keep this discussion between just us.” Sunset sighed, but nodded resignedly.
“As for where that leaves us,” Twilight said slowly, “I’ve travelled to the past before, but that turned out to be a predestination paradox in one timeline. The changes I caused when I travelled back were actually the way the timeline went the first time, which is a slight boost to the idea of this spell moving me from one world line to another since that spell worked differently than this one.” Sunset brightened a little at that, but Twilight continued, “On the other side of the argument, Zecora’s magic in the changeling world told her…” Twilight tried to remember the exact phrasing she had used. “...that we were the real ones? Or that their timeline wasn’t the real one? That it ‘should not be’? Something like that.”
Despite that ominous pronouncement, Sunset actually relaxed slightly. “You’re… actually going to sit here and calmly discuss it with me, aren’t you? Whether or not you should attempt to maybe destroy my world? Only you, Twilight.” She shook her head, with a slightly disbelieving smile.
Twilight flinched. “Well, it’s not quite the same as possibly destroying and replacing a world that Tirek is in the process of incinerating, certainly.” Waving a hoof at the map, she continued, “Do you want to tell me what happened here? Equestria isn’t dying like the other timelines, but it still looks like something went wrong.”
A look of pain flickered across Sunset’s face, but her voice was steady as she answered, “Tirek killed Princess Celestia and Princess Luna before he was defeated.”
There was a gasp from Spike, and Twilight hugged him again as she responded shakily, “But… the sun and the moon?”
“Princess Cadence takes care of that, supported by the rest of the Element Bearers and the Crystal Heart.”
“Princess Cadence is the Element of Magic?” Spike blurted out.
“No, that’s me,” Sunset replied. “Cadence is Laughter.”
Twilight blinked. That actually fit surprisingly well. Making other ponies happy was just such a Cadence thing to do. It was hard to guess at Sunset’s exact past in this world, but being a student (failed or not) of Celestia seemed probable. Twilight suggested hesitantly, “It seems like changing the timeline to bring them back would be something you’d be happy about then.”
“If that’s what you were suggesting, sure,” Sunset agreed. “I might not have had a problem with, say, changing the timeline on the day they died. Everypony would have lost a day’s memories, but been pretty much the same.” She fixed Twilight with a sharp stare. “This is changing everypony’s memories back as far as when you got your cutie mark. That’s long enough that most ponies would be so different that they wouldn’t even really be the same pony. That’s not even including all the ponies more than a few years younger than you. Like Cadence and your brother’s little filly. Princess Celestia wouldn’t want me to prioritise her own life over all her little ponies' lives.”
Twilight sat stunned. Of course the butterfly effect over such a long time would cause different ponies to be born. The idea of this timeline’s Shining and Cadence having a little filly (a few months ahead of her timeline) gave her a concrete image of somepony who would be removed from history if she changed the timeline. And that would not only be repeated for countless others, it had been repeated countless times every time she had changed the timeline up to this! The frankly crazy idea of using Magic of Mass Destruction to kill Starlight by outright destroying everything at Flight Camp would cause less death than simply continuing to reset every time her attempts to stop her failed!
And Sunset wasn’t even finished talking. “You said your zebra friend thought these worlds weren’t ‘real’. That might be a tempting way to label the world when you’re losing a war, but while we’re mourning the loss of Celestia and Luna here, we’re doing pretty well otherwise. I think I’ll take this ‘unreal’ existence over non-existence. Like your world, Princess Luna was rehabilitated, and Discord, Sombra and Tirek were defeated. The map even sent me and uh… you? your alternate? Anyway, sent us to your friend Applejack’s farm to help her with those FlimFlam guys.”
“I think you missed one,” interrupted Spike helpfully. “What about the changelings?”
“There was never an invasion,” answered Sunset. “Long story, but during the weeks of Nightmare Moon’s endless night, one of the ponies who travelled with me on the search for the Elements - and who became one of my close friends who would go on to become one of the Bearers of the Elements - was a ‘unicorn’ who called herself Crystal.”
“You… reformed Chrysalis? She became an Element Bearer?” asked Twilight in amazement.
Sunset replied bluntly, “You reformed Discord.”
“Touché.”
“I just want to emphasise,” Sunset said carefully, “the way that that shows that this world isn’t strictly worse than yours in every way.”
Twilight could see the point Sunset wanted to make. ‘Should not be’ by Zecora’s definition or not, the ponies here weren’t at risk of being wiped out or conquered by evil tyrants, and there were things here that had worked out better than her timeline. And if restoring her timeline meant destroying this one, she would be personally destroying those lives without even the defence that they would have suffered or died even without her interference.
“Here’s my offer then,” Sunset announced. “Stay with us for the moment. We certainly wouldn’t refuse the help of another alicorn here, and in the meantime we put all our resources at your disposal to find a solution to the time-travelling problem that leaves everypony happy. When we find a solution, you should still end up back at the moment you left, so how long it takes isn’t even an issue.” Sunset held out a hoof to Twilight. “I won’t sugarcoat it. You’ll be trusting that I can convince everypony else to trust you, and that’s not a small thing to ask. If you stay until we know it’s safe to our world though, I think I’ve worked out an easy no-risk way to win against Starlight on the next try. What do you say?”
Twilight looked at the outstretched hoof. She was pretty sure it was a genuine offer on Sunset’s part, but all it would take was one pony who didn’t trust her to destroy the spell. A pony with a child who might cease to have ever existed if Twilight cast the spell? Or really anypony worried Twilight might erase most of their lives from history. It was even possible that determined research would discover only that she had a stark choice between destroying this universe and allowing her original universe to remain non-existent. In which case, would that mistrust even be wrong? In fact, the spell even remaining in existence was a threat to this universe in that case, wasn’t it? There were sensible arguments for casting the spell immediately and for destroying it immediately! That was honestly just completely unfair and ridiculous!
Twilight slowly became aware of sounds outside the door. Looking up into Sunset’s eyes, Twilight could see she had made the same realisation and was practically willing Twilight to agree before somepony else entered and complicated the negotiations. Her hoof remained stretched out, waiting for Twilight to take it.
Time slowed to a crawl as thoughts swirled in Twilight’s head. There hadn’t been enough time to think about all the possibilities! There were so many ways this could go, and it all depended on the choice she made in this moment. Every choice seemed to have an interpretation where it risked or outright caused the deaths of worlds, but making no choice was no relief from that!
The door clicked open, and a decision had to be made.
And if there really were such things as world lines, then on a world line very close to this one, Twilight reached out and…
...bumped hooves with Sunset. She would trust that there was time enough to find a way to ensure the safety of both worlds.
...torched Star Swirl’s spell to ashes, preserving this world forever at the cost of ever being able to find her way home.
...cast the spell, abandoning Sunset’s world to whatever its fate was, and…
…planning to destroy Flight Camp in a blast of Mass Destruction so that only a single extra timeline would end before everything was fixed.
...determined to oppose Starlight for as long as it took to fix the timeline.
...deciding to try talking Starlight out of her revenge.
Author's Note
The multiple-choice ending/no ending might not be a surprise to readers familiar with the story's namesake.
If you're not familiar with it, Larry Niven's classic of sci-fi, All The Myriad Ways can be read online here for free.
I did come up with the solution which Sunset claims she has which ~~the margins of this author's note are too small to contain~~ I wonder if any readers can guess. Bonus points for coming up with a simpler and more elegant solution than mine.
The discussions in the story come close to Sunset's solution a few times, but in principle should have worked even in the Season 5 Finale, and no extra information is necessary to reach the solution.
Later Edit:Spoilers for Sunset's proposed solution:
Sunset observed from Twilight's story that when Twilight returned to the past, they moved in space as well as time, and that since there weren't past versions of themselves there, Starlight had to ensure that the rainboom was prevented by their actions on each trip.
Sunset concluded that travelling back to just before the rainboom but to a location where history couldn't be interfered with would restore the timeline no matter what Starlight did while there. The location she planned to use was the location the Crystal Empire would return to, on the basis that nopony would go there before it returned, and after it returned any changes they could possibly make would be covered by the city.
