In the beginning...
...well, there wasn't a beginning. Not yet. There was, however, a place, and it was that place that Twilight Sparkle and her friends walked into, the door behind them swinging closed and vanishing, though they could still sense it with their other senses, still open it at need. There were other doors, an uncountable number ringing the place, visible only to their godly eyes and comprehensible only by their newly expanded minds. Other than that, though, the place had no features; the floor, ceiling, and walls were not simply blank but nonexistent, only a convention of floorness giving their hooves purchase.
There was also a being, though what sort of being Twilight wasn't certain. It looked like a god, but at the same time it didn't; where even the Elements of Harmony had given her a sense of life, this seemed more like a thing, something that... functioned, rather than acted.
"Ooo, what's that?" Pinkie commented, unconsciously mirroring Twilight's verdict. They were both surprised, then, when it reacted.
I am the Caretaker. Twilight shook her head; it hadn't actually spoken, but for some reason she felt that she knew what it would have said if it had. I have awaited your arrival. I am here to assist you, in what ways I am permitted, in the creation and development of your world.
"Hang on a sec," Applejack said, stepping forward, looking confused. "I thought the whole reason the princesses wanted us to do this is that you had a world that needed gods already?"
Indeed, the world exists, the Caretaker responded. Yet it is without form or substance, filled only with the energy of potential. It is up to you to tap that energy, to bring the world into a form that worshipers can inhabit.
"Can we start by bringing this room into form?" Rainbow Dash wondered. "I can't even see!" It was more true to say that there was nothing to see, with mortal eyes at least.
Of course, the Caretaker replied. You have been allotted seven chambers; this one, which you will all share, and one chamber for each of you. You may decorate them however you see fit.
"Sweet," Rainbow Dash said, taking the initiative and throwing her will at the place. Immediately, it became something resembling her former home writ large, a mansion of clouds filled with gaudy yet comfortable furniture, keepsakes and trophies, and images of Wonderbolts old and new. (Somehow, even upon finally becoming one of their number, Dash's hero worship had never let up.)
"Rainbow Dash!" Rarity gasped. "Once again, you demonstrate your utter lack of fashion sense. Clearly I should be the one to design our new home." A hall that would have been at home anywhere in Canterlot flowed out from her, marble and gold, soft carpets and delicate light fixtures—only to meet a barrier between unicorn and pegasus as Rainbow Dash resisted the change.
"And how come you get to pick, huh?" Dash demanded. "I don't wanna live in some stuffy castle my whole life, especially now that it could be practically forever!"
"I refuse to dwell in a... a monument to your own ego!" Rarity said, beginning to strain with the effort of pushing against Dash's design philosophies. She wasn't sure gods could sweat, but she felt like she was exercising, at least.
"Girls!" Twilight yelled, hopping between the two with practiced ease, her own will shoving their energies apart and leaving nothingness in its place. "Each of you gets your own room, and you can do whatever you want with that! Can we at least try to agree on a theme for this one?"
"I figure we should choose something simple. Without a lot of knick-knacks or froo-froo." Wooden paneling flickered around Applejack's feet, though she declined to get into a celestial shoving match.
"Um, some flowers or plants or something would be nice." Fluttershy tried to hide behind her mane, which proved tricky with its added waviness, as grass grew at her feet.
"I know!" Pinkie said. "A balloon castle!" The others looked blankly at her as the floor beneath her turned yellow and somehow rubbery.
"Rarity really is the expert on this sort of thing," Twilight said, leaving Rainbow Dash to look at her in a moment of hurt. "But she's designed outfits for all of us that brought out our beauty, not just hers. I'm sure she can do the same for a space that we can all call home." She turned to look at Rarity, her expression flat, the words "can't she" unspoken.
"Of course," Rarity replied, smiling abashedly. "If you could all just let me know what it is you want, I'll—oh! Oh my." The five had begun to simply will their desires to her. "Well, this does make things faster. Now let me think..."
A new room rippled out from her, a white marble pavilion with a vaulted roof and a smooth tiled floor. Twelve pillars, evenly spaced, supported the ceiling and held sconces casting a warm glow through the pavilion. In every other space between the pillars, there were matching marble walls, while the remaining spaces led into more formless void. On the two pillars framing each void, Rarity placed their cutie marks, designating a space for each of them to call her own.
In the center of the room, Rarity added a soft, luxurious carpet whose hue subtly shifted, taking hints from the former Element-bearers' signature colors, and atop that she placed a broad, circular table—carved from sturdy oak and ringed with six old-fashioned benches. A checked tablecloth covered most of it, but for the moment it was bare of other ornament.
After a moment's thought, and absorbing the impressions of the others on viewing it, she added a few more touches. A smaller, decorative pillar was used on each of the six walls to divide them, and the space on each wall closest to the voids was given over to personal touches. For Fluttershy's, large marble planters, ready to receive seeds, appeared; for Rainbow Dash, twin empty fountain baths came into being.
Rainbow Dash wasted no time willing them to fill with self-replenishing rainbow juice, but Rarity was already moving on, giving Pinkie Pie two niches, which the party pony immediately set to stuffing with balloons and streamers. Twilight received empty bookshelves, which groaned a moment later as Twilight recalled her favorite books. Applejack was trickier; after considering and discarding a few possibilities, she settled on large wooden plaques carved with pictures of apple trees... but a closer inspection revealed that they were family trees, with cutie marks instead of apples. Applejack smiled, made a few corrections, and stood proud.
Last but not least, Rarity framed her space with elegant tapestries, though the designs on them began to flicker as Rarity considered options: her cutie mark? Her silhouette? The carousel pony from her boutique? She wasn't sure what felt quite right. She settled on a single amethyst for one banner and a silhouette bust for the other; she could always change it later if she felt the need.
"Well, what does everypony think?" she said as she turned toward the room—only to find Fluttershy peering into her potting soil and muttering to herself, Applejack tracing her hoof along the family tree, Pinkie Pie dithering over combinations of colors and shapes, and Rainbow Dash already off in the void that was her private space, rapidly turning it into a fantasia of cloud and sky. "...well, don't all thank me at once," she muttered.
"I think you've done a wonderful job," Twilight Sparkle said, blinking across the room to do so. "Though I think you missed a spot." She turned and looked, and Rarity followed her gaze; the Caretaker was still invisible, merely a presence in the room.
"Well, I didn't want to presume," Rarity said. In return, the Caretaker 'bowed'.
You may give me what appearance you wish, it replied. My function is to guide you in your duties to the best of my ability. I have no preferences or desires to be satisfied.
"Hmm," Rarity said, tapping a hoof thoughtfully. "Twilight, what do you think?"
Twilight Sparkle looked distant for a long moment, then shook her head. "No, that wouldn't be fair to him," she said, which confused Rarity, but only briefly. "I want to make it something, but I'm not sure what." She frowned, looking around the room as she thought. "Well, this is embarrassing. An entire world to create, and I'm drawing a blank before we've even started."
If I may be so bold, the Caretaker said, perhaps you should focus on the task of defining the world. Once that is set in motion, you will have time to attend to other needs.
Twilight nodded. "Good thinking." She turned, raising her voice. "Girls, we've got work to do. You can finish decorating later."
The ponies gathered around the table, taking their seats; Pinkie Pie turned hers into an inflatable sofa, which briefly surprised the others, then inspired them to make similar modifications to their own chairs. Fluttershy went with a cozy loveseat, while Rarity opted for an antique chair; Rainbow Dash turned her chair into a fluffy cloud and settled in. Only Twilight and Applejack declined to make modifications, Applejack because Rarity had largely used her preferred aesthetic anyway, Twilight because she didn't much care what her chair looked like as long as it was comfortable.
"So how do we do this anyhow?" Applejack asked, looking to the Caretaker.
Once you have settled on a definition for the world, you will combine your powers and will it to be so, the Caretaker said. It 'gestured', and a formless mass appeared above the table, pulsing with potential.
"Well, what are we waiting for?" Rainbow Dash said. "Let's get started!"
Twilight raised a hoof. "I think we should think this through carefully. Whatever we make, a lot of ponies are going to be stuck with it for a while."
Pinkie Pie chimed, "Oooh, do they all have to be ponies? Because I've got all sorts of ideas for people we could make!"
"That's a good question," Twilight said. "My primary concern is that we not recapitulate Equestria." Rainbow Dash opened her mouth, blinked, gave Twilight an odd look, and closed it again. "At best, our world could only be as good as Equestria, and I feel like it would be both a dishonor to Princess Celestia and... well, lazy."
"We haven't exactly had a lot of other experiences to draw on, sugarcube," Applejack replied.
Twilight smiled. "That's where this comes in." The book Celestia had given her appeared before her, then flashed and sextuplicated, the copies zipping around the table and stopping at each seat. "The book contains information on a bunch of different worlds; we should all look through it for ideas."
"A marvelous idea," Rarity said, flipping her book open and beginning to page through it. Rainbow Dash groaned, but did likewise, and the other ponies opened their books as well.
The next few hours, for lack of a better word, passed quietly. Twilight summoned a stack of parchment and a quill and begun taking notes on the worlds she studied. Applejack opted for a simpler method, sticking bookmarks into her book at various places, while Rarity simply read and absorbed, ideas shifting and forming in her mind. Rainbow Dash, initially unenthusiastic, perked up considerably when she realized that she could make the pictures pop out of the book and examine them in minute detail; she spent some time just zooming about different worlds, taking in the sights. Fluttershy, taking a cue from this, focused primarily on the plant and animal life of each world, making soft noises of approval or dismay as she searched. As for Pinkie Pie, she held her book open sideways and just flipped through the pages as quickly as she could, giggling as she watched worlds blur by like some sort of infinite animation.
At last, Applejack spoke up. "Well, I think I've got some pretty good ideas. How about the rest of you?" The other ponies looked up from their books, then at each other, then at Twilight, who was still staring into her copy of the book. "Twilight?"
Twilight jerked and looked up. "What? Oh! Sorry. It's just so easy to lose track of time in here."
Rainbow Dash snorted. "Like you were any different before. Come on, whaddaya got?"
Twilight glanced at her notes. "Well, I've noticed that the worlds in the book vary greatly in size. Some are much smaller than Equestria, while some are much, much bigger. And their shapes are quite different as well. Some of them are flat like Equestria, but some of them are spherical, some toroidal—"
"Beg your pardon?" said Applejack. Then she blinked. "That's a mite disorienting, Twilight."
"—and some have very strange topography indeed," Twilight finished. "Any thoughts?"
"I like the idea of a big world," Rainbow Dash said. "Like, super big. With lots of stuff for ponies to explore."
"On the other hoof," Rarity retorted, "a smaller world would allow us to focus our attention on making our... followers' lives as ideal as possible."
"If you don't give 'em room to grow, they're not gonna be healthy," Applejack said. "I say we go big and wild, let 'em work to settle the land."
"Ooo, can we make a donut world?" Pinkie wondered. "People will be all 'what's off this way'? Surprise! It's you!"
Twilight glanced over at Fluttershy. "...um, whatever you want is fine," she said.
Twilight sighed, leaning over the table and massaging her forehead with her hooves. "This is gonna take a while."