For fans of my other work, this is a version of Inseparable in which they know about other universes and do things accordingly. The familiar-looking parts aren't quite Deltarune. The rest of this really isn't either one...
Michelle skip-rolled up to her front door, casually tossing a small bit of ball lightning from hand to hand. Her after-school magic club had been a blast, as usual; she'd tossed electrons around before, but not like this. She was good at what she did, a prodigy by any definition of the word, but she wasn't the only talented twelve-year-old attending DJT in Newer Home (Go Snails!) She wasn't even the only one her age who had even more genetic alterations than just the magic cheat code.
It was weird to be home alone, but she knew where everyone else was - Mom was at her day job saving people from themselves (Mom's power SAVEd a lot more people than that), Uncle Azzy had another busy day of chirurgery, Grandma was still at the school doing principal stuff, Grandpa was at the UN (again...), her big sister was in Russia and would portal home in a few hours, her three brothers were at a friend's birthday party, her little sister was at another friend's house (it was easy to have a lot of friends when your last name was Dreemurr) and Dad - well, Dad had his thing to do, too.
She telekinetically slipped off her shoes in the foyer, her socks sinking into the soft carpet as she walked into her room, not wanting to toss lightning around indoors. She had biology homework to do (it was a final-version day, Mom would SAVE that night), but she needed a break. She took off her purple backpack and set it down into the corner of the room, surprised at how dark it was- it'd been sunny when she got in. She flicked the lightswitch, but her hand passed through empty space where she'd expected it to be.
Then the floor wasn't there anymore, either.
She briefly hovered in place, startled, but no mage could keep that up forever. Instead, she looked down, aiming for a pile of papers visible in the blackness, and gently levitated down next to it, her dress fluttering around her as she did.
Wait. Her dress?
She felt the silky texture of the bright purple frock (it looked like something out of an anime), felt the ribbons in her hair, wiggled her toes in the comfortable, slipper-like shoes. She hadn't passed out on her bed, then - she'd had lucid dreams before, but they were nothing like this.
The idea that she might have panicked never even entered her mind. There was a rule she followed, a rule her parents never really had to teach her: If you don't know what else to do, think.
At least, wherever she was, she had breathable air and quantum mechanics and everything else that human beings needed to not suffocate or explode into unbound energy - or the transition had changed her into something that didn't need those things. But that was rarer, and she still felt like herself. Lighter, though. Her phone seemed to be her only possession to survive the transition unscathed, and she pulled it out of her dress pocket- fortunately, it had those- and gently tossed it from hand to hand. Yeah, gravity was about 4/5 that of home.
Almost certainly another universe, she figured, although she theoretically could have been teleported to another planet or something. Still, her altered clothes and the pile of papers suggested that she was in one of the thirties, a category of pocket universes whose existences were based on that of their visitors. Her magic still worked, which meant that she probably wasn't in one of the high thirties- but a horrible idea struck her. "Hello?" she asked out loud. "If you've brought me inside you, I'd really like to know why." Silence was the only response, and she breathed a sigh of relief. Probably not a consciously self-aware universe, then, not one of the fifties. Those things, her father had once explained, tended to cause problems. She focused on the pile of papers, trying to turn them into flowers - it didn't do anything, which ruled out Type 31(a), consciously mutable. Good. That category tended to evaporate quickly once somebody tried to make a square circle or something. She also doubted she was in a 32, which wasn't directly mutable but would respond in very strange ways to her thoughts. It could be a 31(b), subconsciously mutable (not good either) or a 31(c), supraconsciously/SOUL-mutable, but she guessed that she was either in one of the 33s, mentally created, or a 34, mentally and environment-created. (A type 35, purely environment-created, probably wouldn't have changed her clothes. Then again, universes didn't always fit neatly into categories.)
She flipped open her phone. No Signal - she'd expected that. You couldn't make a phone that could do that, at least not with her home's physics. She opened her favorite app and scrolled down to tap one of her most basic spells, a familiar string of syllables came out, and a globe of low-energy amber light appeared above her head. She nodded in approval. Verbal spells were also a go.
The next piece of information she really wanted, although it technically wasn't really important yet, was how she got there. She tried to think of anyone from her school who could have pulled off a prank that involved teleporting her to another universe, and came up empty- there were a few kids who'd probably want to, just to say they did, but to set something up inside her house? Maybe Mom or Dad could have done it- Shelly really had been interested when Mom talked about her adventure in the Underground (a since-evaporated type 24(a)(4), a sub-universe that altered the properties of its home universe on its creation and forcibly contained a class of beings - i.e. a prison universe). They wouldn't, though. Dad's obstacle courses weren't like this, and Mom just... wouldn't, nor would the rest of her family.
Then again, if her youngest brother Mander were behind this, she was pretty sure that Mom would actually spank him for it.
Right, next up- find out just what she had "fallen" into. There was nothing under the pile of (disappointingly blank) papers, and the only visible way to go was a light down a corridor some unknown distance away. She felt one of the utterly black, unreflective walls, and the floor; both were solid and smooth. (She was quite glad that the outfit had come with light, silky gloves; despite how much she knew that she shouldn't care in a Type 33 or 34, she really didn't want to be touching random objects with her bare skin.) She pointed with her finger and traced the walls with a low-power violet laser, a trick that her older brother Jimmy had mastered much earlier in life and eagerly taught her. She couldn't find any openings in the walls that way, though, and the ceiling seemed to have sealed itself above her. She considered maybe knocking on or breaking through a wall, but she didn't know what was on the other side of the walls nor how thick they were- for all she knew, there could be nothing on the other side. The pile of papers were illuminated of their own accord, not from a source, and she noticed with a touch of alarm that she, herself, seemed to be glowing with reflected light from no source as well, and she dispelled her light globe after realizing that it wasn't helping. She kind of wanted to figure out why, but figuring out the physics of this place would have taken her at least a few hours and she wanted to be home before that.
She clicked her tongue, listening for echoes and not hearing any. Down the hallway it was, then.
It wasn't long before she spied something, a pale, glowing star, a faint light that Michelle suspected was not entirely made of photons. She realized what it was at once. Mom didn't need SAVE points anymore - her DETERMINATION let her SAVE anywhere, anytime in her home universe - but she'd explained to her daughter what it had felt like, the DETERMINATION welling up within her, the light that only she could see. Michelle briefly considered the pros and cons but chose to take the opportunity, reaching out, feeling it flow into her, saving the state of the universe. She didn't know what might happen if she kept a SAVE in another universe, but she did know that without one, she could actually be killed. That particular train of thought took her somewhere she didn't want to go. Dad had to be home when Mom LOADed and SAVEd for a reason. Not being home for the first could make a copy of him- which was, for multiple thaumaturgical reasons, an incredibly bad idea despite how productive it might have seemed- and the latter could easily put him out of existence entirely. (Dad had killed at least three otherwise invincible godlings that way, getting them to follow him home right before Mom LOADed, thus erasing them utterly.) Maybe Mom could LOAD her back in at home if she perma-died here, but she didn't know what she would or wouldn't remember after that, and she definitely didn't want to forget any of this.
As she continued, she walked between strangely geometric rock formations, where the walls were solid brown something instead of solid black nothing. Eye cutouts were engraved in the walls, and dark cutouts that looked almost like pools of ichor were embedded in them, almost in the shape of a dog's snout. That thought took her aback. If Dog Himself were directly responsible for this, her dad was going to go ballistic. Her whole family would probably freak, actually. It was too dark to see what, if anything, was in those holes - shining a light did nothing - and so she continued, perturbed. At the edges of the cliffs far above the canyon she was in, she noticed wobbly things with red heads, about the color of erasers, and their stalks were different colors; they shook as she passed beneath them, startling her. They looked almost like colored pencils - which, she realized, was what she had quite a lot of in her room. A definite hallmark of a 34, and because it looked like an 'adventure' setting, she pegged it as almost certainly a 34(b) - mentally and environmentally derived with a significant elsewhere-created component. It was feeling a bit too linear, though. She liked to write on lines, but she wasn't all that keen on being forced down one. She decided against levitating all the way up to the pencil-things, though; she had to save her energy and wished that she were still wearing her roller shoes.
The markings on the wall provided some welcome relief, a sign that somebody was around and this wasn't some empty hell. A puzzle of some kind, apparently. It would have been nothing for her to float over the gap in the floor; she could probably have made a running leap even without the aid of magic. Still, it was the principle of the thing, and if she ever met the puzzle's creator, she didn't want to have cheated.
The numbers 7, 8, and 9 were crossed out on the top row, then the number 260 was shown below that in black, then the number 1 below that in red. Three holes were embedded in the wall, each with the emblem "x, +" and then a number of 2, 3, or 5. Puzzled, she puzzled over the puzzling puzzle. Was she supposed to get to 260 by multiplying, then adding each of these numbers? She didn't see how. Maybe she was supposed to get above 260 without having any digit be a 7, 8, or 9? Oh, she could do that. She pressed the 5 button, and the red number became 13 rather than the 10 she was expecting.
After a brief moment of confusion, she figured out what she was supposed to do. She was starting to like this universe, even if it was a little easy.