Reality folded back into being and Twilight Sparkle landed on a familiar hardened floor. She looked up and saw the familiar crystalline walls and the bookshelves which ringed around the room. The tables and the mirror portal apparatus stood in their usual places.
Crystal Faire, who stood beside her, turned and walked toward the chalkboard. She used her magic to lift the eraser and began wiping the board clean.
Twilight trotted behind her and, after taking one last look at her work, said, “So, I was thinking…”
“Yes?” Crystal replied.
“That thing where the timelines snapped together when you came to visit… Everything threaded together such that I was still the only Twilight, right?”
Crystal kept her eyes toward erasing the board. “You’re calling that concurrently-crystallized, right?”
Twilight nodded. “That’s… right. I’m… sure that I said it in some conversation that we might have held a few minutes from now.”
“Of course. What about it?”
Twilight leaned in close. “We should try it again so that we’re sure it’s consistent. And we need to know what caused it to happen in the first place.” She pointed to herself and said, “I was displaced, remember?”
“Yeah.”
Twilight stroked her chin. “I was wondering if that had anything to do with it. We should also see if displacement continues even if you return to your original timeline. And also—”
“We could test for all that, sure, but—” Crystal stepped back, nodded at the now-clear chalkboard, and then looked over, “—let’s not get ahead of ourselves.”
Twilight blushed and giggled nervously. “Sorry, I just have so many thoughts. I’m so excited! I can’t wait to get started!”
Crystal chuckled. “I’m sure, I’m sure. But… before that…” She turned and trotted toward one side of the room with the eraser still in her magical grasp. “There’s something I’ve been meaning to see about.”
Twilight tilted her head. “Oh? And what’s that?”
Crystal stopped a few meters away from the bookshelf and tossed the eraser up and down. “Well… it’s something I noticed. I’m going to do something here just because I want to see where this goes.”
Twilight raised an eyebrow.
Crystal lobbed the eraser toward the bookshelf. It flew a couple of meters before it bounced off something invisible and clattered to the floor. Whatever it hit made a startled cry.
Twilight gasped. She eyed the cloud of dust that the collision had thrown off the eraser and watched as it settled into the form of a pony.
Crystal snickered.
Twilight narrowed her eyes. “Starlight Glimmer!?”
Starlight Glimmer faded into being and wiped some chalk dust off her muzzle. “What the hay! You knew I was there?”
Crystal snickered even harder.
“Starlight!” Twilight exclaimed as she rushed over. “How the…? You’ve been here this whole time?”
Starlight met eyes with Twilight and blushed. “Uh… yeah… All day, actually.”
“That was an invisibility spell. I…” Twilight blushed and grumbled, “I didn’t even know you could do that.”
“Well, I wanted to know what your top secret stuff was…” Starlight rubbed the back of her head with a guilty frown across her muzzle. “So… uh… I snuck in as you were setting up, and I was, you know, kinda hoping to leave a lot sooner.”
“Because she teleport-proofed the room, right?” Crystal asked.
Twilight frowned. “Yeah, I did. Starlight, I can’t believe you. You were spying on me!?”
“Well…” Starlight began.
“I can’t believe you! How could you spy on me!?”
“I was worried! I wanted to know what was nagging at you so that I could help you, maybe.”
Twilight pinched the bridge of her snout and sighed.
“Well, in fairness,” Crystal said as she turned around, “it was also probabilistic anyhow. There were timelines where she didn’t spy on you. I just happened to pick one where she did.”
Starlight blinked and frowned at Crystal. “Uh… what?”
“Starlight…” Twilight began, “I… appreciate that you’re thinking of me. But, really…”
Crystal chuckled and leaned in. “Plus, Twilight, you did enchant the room so nopony could spy on you. So… you were obviously expecting something.”
A long pause passed between the three of them as Crystal and Starlight stared Twilight down.
Twilight went red in the face and swallowed. “Err… Well, that’s a fair point, I guess.”
Crystal turned. “So, Starlight, the question is how much of what you heard did you actually understand.”
Starlight’s eyes flicked from side to side as she hummed thoughtfully. “Well… I uh… I understood some of it. I guess. I don’t know.”
“Thought so,” Crystal said.
“I mean, I’ve done some stuff with timelines before, believe it or not,” Starlight said, chuckling. “But, uh, what you were talking about got really stupid really quickly, and I got lost. Also, I think that there were things that she said that I couldn’t hear.”
Twilight frowned.
“But… when you appeared out of nowhere a couple minutes ago, the two of you talked… Twilight…” Starlight said, turning, “you said something… something about having trouble looking at reality. At us, even.” She raised an eyebrow and asked, “What gives?”
Crystal looked over with a raised eyebrow.
Twilight sighed. “Well… You see… There are other realities out there. They are so much like this one, but they aren’t exactly the same. I’ve…” She chewed on her next words for a moment. “I’ve been in them at one point or another.”
Starlight raised an eyebrow. “Oh, really? I mean…” She grimaced. “I mean, we’ve been to alternate timelines before, you and I. But they were radically different—”
“These aren’t,” Twilight interrupted. “They’re only different in the smallest details. It’s hard to distinguish them from one another.” She turned to Crystal and smiled. “But I think I’m getting the hang of it.”
Starlight turned to Crystal. “And you’re some sort of time traveler?”
“Of a sort,” Crystal replied.
“I mean, I remember you from several days ago,” Starlight said. She scratched her head and mumbled, “I guess some things make sense now.”
“Indeed. As a matter of fact, the two of us just returned from visiting some other timelines. Although, I suppose for you, not even an instant passed, hmmm?”
Starlight scratched her head. “You jumped spots to me.”
Crystal smirked. “Quite. Anyway, this has been fun, and all… but…” Crystal picked Starlight up with her magic and floated her toward the door. “Twilight and I have some business to do.”
Starlight flailed about. “Like what!?” she cried.
“Just some experiments that the two of us want to run,” Crystal said.
Starlight frowned. “Okay?”
Twilight scratched her chin. “Well, Starlight… since you are here, though… I think you might be able to help us out.”
Both Crystal and Starlight blinked and looked back at her and asked, “What?”
Twilight stepped forward. “Well, you have experience with other timelines, after all. Not the way that the two of us do, sure…”
Crystal raised an eyebrow. “Are you sure?”
Starlight puffed her cheeks out and then lit her horn. She teleported out of Crystal’s grasp and reappeared a meter away.
“I’m positive,” Twilight replied. “Starlight is a good friend and I know that I can count on her to help us out.”
“…Even though she doesn’t yet grasp what we’re dealing with?” Crystal grumbled.
Twilight giggled and raised an eyebrow. “Crystal Faire… You know what I’m about.”
Crystal rolled her eyes. “…I do.”
“Besides, she has some experience. That’s a good thing!”
Starlight puffed her chest out and smiled with pride.
“I suppose it can’t hurt.” Crystal hummed whilst nodding from side to side. She paced about for a few moments, her expression loosening with every step. “Actually, it’s given me an idea or two. Huh, I think this could work out.”
“I’m so glad to hear you agree!” Twilight turned and hugged Starlight. “This is exciting! We’re going to do an experiment together! I’m glad you could join us.”
Starlight chuckled. “Well, happy to help…”
“So, now we have three experts on time, at least,” Twilight said. “That should be helpful. I wish we had more.”
Starlight hummed as she scratched her chin. “Maybe we should ask Spike? Although I think he said he was going to Rarity’s.”
Crystal stared off into space for a moment. “Yes, he’s there right now. Oh…” She smiled. “It looks like he’s having a great time over there. Phenomenal, even.”
“Oh really?” Twilight asked, tilted her head.
Starlight threw her head back and laughed. “Well!”
“Wait,” Twilight said, “how do you see it turning out?”
Crystal stared again. “I see… well, there’s a significant probability of it being a really nice dinner. I think I’ll even... make that probability a certainty.”
“Well then,” Twilight giggled, “maybe I’ll let my little casanova have it this time.”
Starlight clapped her hooves together. “Right! So… so… yeah. That does just leave the three of us.”
Crystal hummed as she drew circles on the hard floor.
“It’s a shame. I don’t know anypony else who knows even a bit of time travel,” Twilight said.
“Me neither,” Starlight agreed.
Crystal drew more circles into the floor. Her lips puckered and unpuckered as she thought. “I… don’t personally know anypony either. But—” she looked up, “—there is somepony that I know of who springs to mind…”
* * *
The mirror portal shimmered, and a mare of amber coat emerged. Her hind hooves touched the ground but she, strangely, stayed upright. She wobbled for a second and then finally dropped onto all four hooves. Both her curly mane and tail, striped with red and yellow, bounced as she landed.
“Sunset Shimmer!” Twilight exclaimed as she bounced in place. “Hi!”
Sunset Shimmer cracked some joints in her neck and then waved. “How’s it going?” She turned. “Hey, Starlight, how are ya?”
Starlight, hesitantly, waved back. “Uh, hi! Do… Have we met?”
Sunset raised an eyebrow. “Uhhhhhh… yeah. We’ve met. Don’t you remember?”
Starlight frowned in response. “No…?”
Crystal wrapped a hoof around Starlight and pulled her close. “Starlight Glimmer, meet Sunset Shimmer. We are in a timeline in which the two of you have met.”
Sunset’s expression fell. “Uh, excuse me?”
Starlight blinked and glanced at Crystal with a befuddled frown. “We’re in a timeline where…” She jumped and sharply gasped. “Wait. That’s what that teleport was!?”
“Yes, that was me bringing you into another timeline.”
Twilight nodded in agreement.
Sunset tilted her head in confusion. “What timeline, then? Which one are you from?”
Crystal stepped forward. “Ah, Sunset, we’re not from the timelines that you know. Actually, our definition isn’t the same. What you know as alternate timelines are just sub-components of a single timeline in our definition.”
Sunset scratched her head. “…Oooookay.”
“As I understand it, you have already dealt with the Nameless and some things related to it.”
Sunset nodded.
Twilight raised an eyebrow. “The what?”
Sunset’s eyes widened and she looked between the two. “Really?”
Crystal nodded.
“Wow. That’s… well…” Sunset scratched her head.
Crystal motioned with her head toward Twilight and Starlight and said, “Why don’t you tell them a little bit about it?”
Sunset straightened up. “Well… there’s this thing under Canterlot. We called it the Nameless. It’s in those caves there. It’s a monster. And, well, some really bad things happened to you,” she said, pointing to Twilight, “and—”
“What sort of bad thing?” Twilight interrupted.
“You don’t wanna know,” Sunset sharply replied. “Either way, during all this, I also started dealing with an infinite number of realities. I used that to master the problem that I was dealing with.”
Crystal smiled.
“I later met some ponies who… they’re a different type of pony entirely. And their queen, Adamantine… she was really nice, but she kinda got backed into a corner...” Sunset frowned and kicked the ground. “I wish I could have done more for her.” She shook her head. “But, during that time, I got involved with alternate timelines and all that.”
“I see,” Twilight replied.
Sunset glanced at Starlight and bit her lip. “I’ll… I’ll spare you the details on that, but whatever.”
“Interestingly enough,” Crystal said as she turned to Twilight, “everything that she just described, these things with the Nameless, happened in my home timeline too. And it is something I have accounted for and built filters around.”
“Fascinating,” Twilight said, stroking her chin. “I can see why you thought of her.”
Crystal chuckled. “More than just that.”
“That’s kinda cool,” Starlight said. “Infinite worlds and alternate timelines, huh?”
Crystal stepped forward. “I think it’s time that I actually introduce myself. My name is Crystal Faire. I’m Twilight’s niece, daughter of Princess Cadance and Prince Shining Armor, and time slider.”
At once, both Starlight and Sunset gasped. “No way! You…” Starlight squinted as her eyes ran over every inch of Crystal. “By Celestia, I thought I vaguely recognized you. Holy hay, you are…”
Sunset tapped a hoof against her chin and looked Crystal up and down. “Huh, that’s interesting. Time slider, huh?”
“Yes,” Crystal replied. “And as to why I’m here, why all of us are here, is that Twilight and I want to run an experiment. Starlight here has agreed to help, and, Sunset, we could use your assistance as well.”
Sunset continued stroking her chin. She cautiously narrowed her eyes. “Hmm, and what exactly are you experimenting?”
Crystal smirked. “The multiverse. We intend to figure out exactly how these infinitely many realities work.”
Sunset frowned. “You can actually do that? Are you sure?”
“I am. And, as we experiment, I will show them to you.”
Sunset stood in silence for a few moments. Her eyes remained mostly on Crystal, but they briefly meandered over Twilight and Starlight. “How long will it take?”
“I don’t know, but you’ll be back in an instant.”
Sunset stroked her chin for a few moments more. Finally, she smiled.
* * *
Twilight packed the sheets of paper into a neat stack and placed them on the table. She turned and repositioned some sticks of chalk on the edge of the chalkboard. She then turned and closely scrutinized the seven lined-up images before her: each looked like several timelines diverging from one point at the bottom. Despite how closely she looked at the images, she couldn’t find anything different about them.
Crystal trotted up, magic coursing through her horn. “Good to go?” she asked.
“I am. Just to make sure one last time,” Twilight said, “this one on the left is me.”
“Yes. If these lines disappear once I travel to other timelines with Starlight and Sunset, then,” Crystal shrugged, “we’ll know that I can’t sustain spells across timelines.”
“And if that happens, you’ll just let me know what you see when you get back and we’ll compile our notes.”
“Right. These lines cover about one hour, so we shouldn’t have any problems seeing anything.”
“Great,” Twilight said, looking past Crystal as Sunset and Starlight trotted up. “Are you two ready?”
Sunset nodded. “I think so. This is going to be interesting, huh?”
“Absolutely,” Twilight replied. “You’ll get to see how all this works.”
“And how she works, I guess,” Starlight added.
“I chose these,” Crystal said, motioning toward the timelines, “because they’re quick fixes. Shouldn’t take me thirty seconds for any of them.”
“It’s efficient, at least.” Twilight lit her horn and floated a piece of chalk to her side. “I’m ready.”
Crystal nodded and turned to the other two. “Let’s get started then. Gather around.”
Starlight and Sunset drew close to Crystal. Crystal shifted, and in a single loud bang, the three of them instantaneously vanished.
Twilight winced at the sound, but the ringing quickly subsided. She then looked over and found that the timelines which Crystal had formed with her magic still floated in the space before her.
She felt her hairs stand on end and, slowly, a smile spread across her face. “Okay!” she exclaimed. She whirled around to face the board and started to write. “Crystal can sustain spells across timelines.”
She twirled the chalk in her magical grasp and turned back to the timelines. “Alright! Now… let’s see what happens!”
She pointed the chalk at the set of timelines on the far left. “The three of them went from here to here,” Twilight said, pointing her chalk at the line right next to it. “Meanwhile, the one I’m in…” She looked it up and down; it appeared crystallized but not as hardened as it should have been.
She hummed and set the chalk down. “It’s… quasi-crystallized. That signifies time-locked segments. Hmm. Why is that?”
Twilight chalked some words onto the board. “I’ll just make a note of this for now.”
She leaned forward to examine the first line again. Her eyes drew toward the bottom where she saw the makings of a crystallized bit. Her muzzle curled into a frown. Her eyes shifted to the second set and saw a crystallized bit forming at its bottom as well. On closer inspection, she saw the set of lines furling together and meeting at the top of the newly crystallized sections.
“This is her threading the timelines together. Everything after this point can still diverge, but then she’s threading those diverging timelines together too.
“So, both my timeline and the one they went to are crystallizing. What does this mean? Crystal is sustaining this image spell from another timeline. Time is passing for her in that timeline…”
Twilight scratched her chin and looked at the two timelines again.
“I’m seeing that passage of time from here.” Twilight gasped. “That… that makes sense! She herself is in another timeline but she is reaching into this one via the image spell, so it’s like existing in both at the same time. So whatever amount of time passes wherever she is… the same amount of time has to pass here as well!”
She whirled around to face the chalkboard again and started to write. “This is a fascinating result! I didn’t even think we’d get anything like this!”
Twilight shivered. We aren’t even a minute into this and already…! What else are we going to find!?
She punctuated the end of her sentence by hitting the chalkboard with the chalk itself. She set the stick back down and turned back to the images.
“Anyway, I suspect that Crystal is done in this second timeline. Now… she’ll travel with Starlight to this third timeline and leave Sunset in the second one.”
In an instant, the second set of timelines changed from a quasi-crystallized state into a mostly solid and viscous one. The bottom sections still appeared entirely crystallized but Twilight could see the boundary where, evidently, Crystal had departed.
“Okay, this timeline, which Sunset is still in, just turned concurrently-crystallized. If I am correct… all these diverging timelines will snap together into one single timeline when Crystal returns to pick her up.”
“Nonetheless, this pretty much confirms the hypothesis,” she said as she wrote her thoughts on the board. “As to why this happens at all… it would conserve the number of Sunsets in the multiverse, I think, just like the amount of myself was conserved.”
Twilight turned to the third line and watched the bottommost parts crystallize. “That’s Crystal there.” She stole a glance at her own timeline which was still slowly crystallizing. “The passage of time still rings true despite the fact that Crystal changed timelines.”
Twilight sat there in silence for several moments. The images changed again as the third set of timelines, the timelines which Starlight was in, turned viscous. Concurrently-crystallized, Twilight noted.
The second set of timelines, where Crystal had once left Sunset, folded together up to a certain point. Everything after that hardened into an almost-crystallized state with the bottommost parts slowly completing the process.
Twilight nodded. “Crystal left Starlight in those timelines and just returned to pick up Sunset. Now, she can take Sunset to the fourth set of timelines here, which is Sunset’s home. Crystal has nothing to fix there. And now Crystal is going to leave Sunset in her own timeline,” she said.
The fourth set of timelines turned viscous as the fifth set right next to it started to crystallize from the bottom up.
Twilight frowned and placed her chalk against the board. “Well, that probably confirms it, then. Displacement is permanent. Once multiversally significant, always multiversally significant. And if you are displaced, then any timeline you travel into will concurrently-crystallize and eventually thread into one single timeline just like it did with me.”
She turned to the fifth set of timelines and examined them closely. “Alright. Now… Crystal is going to an area of high gravity. Let’s see how relativistic time dilation comes into play.” She readied her chalk and watched as both her own and the fifth set crystallized from the bottom up. “It doesn’t matter what timeline Crystal goes to; the passage of time between her and her spell, thus between me and her, is normally constant. But, if relativity holds, my time should go by faster here.”
She giggled and shook her head. “Some future me apparently designed some starship in this one, didn’t she? ES Harmony, I think?” Twilight sighed as many images swam through her head, each bringing a smile to her face. “Wow, to go see black holes and neutron stars up close! I should have gone.”
She watched the two sets of timelines closely. Her own set of timelines continued to furl up and crystallize as before, but the other seemed to do nothing at all. No, there was something happening, but Twilight had to lean in very close to see it: the set of timelines that Crystal was in was doing the same thing as her own but at a snail’s pace.
Twilight flip-flopped between the two timelines and then stood up. “So, that’s it. Crystal’s time has slowed down, and it shows! That’s why hers is crystallizing at the rate it is: it’s crystallizing at her speed. Meanwhile, mine is still crystallizing but it’s because of the spell. So, really, it’s still her speed.”
Twilight wrote the results on the board and then took a step back. “So, to summarize this series, timelines crystallize at the rate in which Crystal experiences time. That seems to suggest…” Twilight placed a hoof on her chin. “It’s like… Crystal Faire is the metric by which these timelines evolve.”
She clopped her hooves together and smiled wide. “Fascinating! And it… it makes sense! She’s the one that’s affecting alterations.”
The fifth set of timelines froze, and a sixth began to crystallize. Twilight turned her attention to the latter. “And then… Crystal is going into this sixth timeline and she’s going to leave her cloak there. Sunset and Starlight have prompted the timelines to turn concurrently-crystallized. Let’s see if an inanimate object does as well.”
The sixth set of timelines turned viscous as Crystal, Twilight presumed, hopped to the seventh and final set of timelines.
Twilight hummed. “Okay, so displacement also occurs with inanimate objects too. Her cloak is multiversally significant. So, basically, anything which travels to another timeline becomes multiversally significant.”
She glanced at the final set. “Now Crystal is going to sustain a spell just like this one,” she motioned to the images before her, “and then she will jump back to get her cloak.” Twilight pointed to a spot within the unfurled sections. “This is about thirty minutes from the time she left, right? Let’s see if these infinitely many timelines snap together into one effective timeline, just like with what happened to me.”
Sure enough, half the set suddenly folded together into a single line. Only the last bits near the top remained unfurled.
“So, that confirms it. There were an infinite number of timelines which the cloak occupied, and then Crystal visited one of them, and everything threaded into that one timeline. Simply incredible…” she whispered as she wrote her conclusion on the board.
Twilight hummed. “And now, Crystal should travel back to this seventh set which she’s sustaining that second spell in. Look at that, it’s turned quasi-crystallized, just like my own. Nonetheless, thirty minutes out should do.”
Twilight watched in silence at the images remained unchanged. The sixth set, which Crystal occupied, continued to crystallize at the rate which it had done so before. Seconds ticked by, and eventually Twilight frowned.
She scratched her head and leaned forward. “Okay… thirty seconds?”
Again, the images remained unchanged.
“Interesting… Twilight cooed. “Okay, Crystal… can you hit it right on the dot? Travel to the same moment that your spell is in.”
The images changed. The bits at the tops of both sets turned hazy as, Twilight presumed, Crystal hopped from the sixth set to the seventh. Twilight immediately jumped in response.
She whirled to face the board. “Okay! So that actually worked that time. I mean, obviously, we should have expected this since everything in the future was quasi-crystallized. I wonder why…?”
She took a moment to write down the result on the board and then turned back toward the images again. “If I had to guess… it has to become quasi-crystallized because, even if you aren’t physically there, you still have some presence there. And you can’t exist in two time periods at once.”
Twilight heard a loud bang and whirled around to find Crystal standing before her.
“That’s what I was thinking,” Crystal said. “It must be a failsafe of some sort.”
Twilight turned back toward the image. “Look at that; it’s quasi-crystallized again. You’re here, but your spell is there. It’s preservation of continuity.”
“That’s what it looks like.”
Twilight scratched her head. “I wonder… do you think something along this line might explain that discontinuity we talked about?”
Crystal snorted and shook her head. “I can’t really say right now. There’s still too much about it that we don’t know.”
“Right…” She turned back toward the images, looking over each of the seven sets of timelines again. “Alright, I think that should be everything.” Her eyes centered on the last set of timelines again. She looked at it closely. “Actually…”
“Hmmm?”
“Discontinue this second spell right now. I want to see what happens.”
Crystal nodded and leaned forward as well. In an instant, the seventh set turned from almost-crystallized to hazy and undefined.
Crystal hummed. “Okay, this makes sense. I don’t have a presence there anymore, so it’s free to unthread and diverge.”
Twilight clopped her hooves together and smiled wide. “Fantastic. I figured that would happen, and it’s good to know that I was right!”
Crystal nodded. “Alright, anything else?”
Twilight examined the set of lines again and then, eventually, shook her head. “Nope. I think we’re done.”
Crystal clopped her hooves together too. “Great! So then… I can go gather up Starlight and Sunset and we can review what all we’ve learned.”
“Right. Uh… before you go… I want to ask you something really quick.”
The magic coursing through Crystal’s horn faded. The sets of timelines which had been next to the chalkboard faded into nothing. Crystal looked over her withers. “Yeah?”
“Can you come by tomorrow? I’m going to need your help with something.”
Crystal raised an eyebrow. “Really? What?”
Twilight blushed and rubbed her foreleg. “I… I need to get some things off my chest. I’ll need your help.”
Crystal’s mouth formed a slanted line. She hummed and kicked the floor. Eventually, she replied, “Sure. Actually, I guess I’ll take Sunset home and then come back and just stay the night. I need to get some sleep, anyhow.”
“You’ll help me?”
“…Yeah.”
Twilight nodded. “Okay. Thanks, Crystal. Go get them so that we can get back to business.”
Crystal nodded. She shifted and disappeared in a loud bang. A simultaneous bang sounded from a meter away from where Crystal reappeared with both Sunset and Starlight by her side.
The latter two blinked, looked around at their surroundings, and then looked at Twilight.
And Twilight smirked.