You didn't go far. Your shortcut took you just upstairs, to Alphys' room. You strode over to her desk and tore open one of the drawers; the one you knew contained her blueprints. Sure enough, the drawer was full of them. Without stopping to look at which ones were relevant to you, you scooped them all up into your arms and stepped through another shortcut.
This time, you were back at the hotel, your magic pounding in your bones despite your outwardly calm appearance. There weren't many people in the lobby at one in the morning, but those who were gave you even stranger looks than before. You hefted up your armful of blueprints, holding them securely and glaring at anyone who might've dared to ask you what you were doing.
No one asked.
Your bones rattled softly as you returned back to the Core. As soon as you were far enough in that you knew no one would follow you, you dropped the blueprints and knelt down on the floor. None of them were labeled, so you had to open them all in order to find the ones you needed. The warbling, crackling sounds of long sheets of paper being unrolled only heightened your already frayed nerves. You realized halfway through that you weren't actually paying any attention to what the blueprints were telling you, and had to force yourself to stop.
You sat back, your spine hitting the metal wall of the Core. Your breath came in harsh gasps as though you'd run a marathon.
"What am I doing?" You muttered to yourself, grinding your palm into your forehead just hard enough to hurt. You had no idea how to deal with what had just happened. This… the Core… was easier. You laughed in a way that some people might have thought was insane. You knew you were fucked in the head when dealing with Gaster's problems was easier than taking care of your own.
A part of your mind nagged at you not to do this. To just suck it up, go back to the lab, and face the consequences. But another, louder part of you really did not want to do that.
I wanted more time to find Gaster… well, now I have it. You reasoned with yourself before slowly crawling back to the blueprints.
You looked over them with more care this time, and gently rolled up the ones that were useless to you. Many of them were plans for Mettaton's new body, or plans for the DTEM, or plans for modifying the DTEM to suit your own needs. You looked over the ones which had to do with the Core with more scrutiny. With Sans' knowledge, these blueprints were no longer meaningless jargon to you, but a complex and, frankly, beautiful map of the Core's inner workings. For hours, you sat there, pouring over them. Looking for just what exactly could have gone wrong to cause the Core to fail.
The answer was… quite a lot. The Core was incredibly complex and was built on the concepts which Gaster had previously explored with the time machine. There were many things that could've gone wrong to cause a catastrophic failure, from the input of an incorrect data point, to the shortage of a single wire. As you continued to muddle through the complicated science behind it, you grew more and more incredulous. Gaster built very few, if any, safety measures into the Core. There were no backups, emergency exits, or even alarms. With those factors working against him, Gaster had to have known it was possible, even likely, that something would go wrong. It was, to put it briefly, sloppy work.
Why, though? Was it the lack of funding? The urgency to get it done as soon as possible?
Aside from that, reading the blueprints gave you some insight into how the Core generated enough energy to travel interdimensionally. It seemed that powering the Core was a two-step process; first, Gaster had used geothermal energy to get things started. But, when that wasn't enough, he'd started using energy from… somewhere else. This was, by and large, the most complicated part of the blueprints, and it took you several careful read throughs before you finally understood what was going on. It seemed that Gaster had found a way to drain energy from shortcuts, the very same wrinkles in space that you used for travel. He didn't call them shortcuts, but "wormholes," and it didn't seem like he could see or use them as naturally as you could. He'd simply figured out that they were there, invisible, and used them to his advantage.
In a way, this was more impressive to you than if he had been able to see the shortcuts. How did he figure out that they were there? Had Sans told Gaster about them when they'd worked together? But, if that was the case, why did Gaster call them something different? You would've given your right wing to see Gaster's private notes, or just to remember anything from that timeline.
At any rate, this explained why there were no shortcuts in the Core. The machine had drained them all dry before, or during, its inevitable failure.
As you moved on from the paper you'd been staring at, you noticed that the last few blueprints were written in wingdings, too. They didn't have anything to do with the Core, but the language caught your attention nonetheless. When you looked more closely, you saw that there were some notes written in English in the margins, too, and you couldn't resist taking a look.
It was all about souls. But not human souls, like you might've expected. Monster souls; specifically, what they were made of, and how to replicate them. You furrowed your brow as you read, confused. This had nothing to do with anything that you knew Gaster had created, but it was surely his writing. Someone must've taken interest in the subject matter, because the notes in English were clearly written by someone else. Someone who didn't know wingdings, because their notes consisted mainly of inferences they'd made from the pictures…
"Alphys." You said out loud once you realized. Now that it occurred to you, you did recognize that sloppy chicken scratch. Perhaps Alphys had found these blueprints and used them as the starting point for her own soul research.
Soul magic wasn't exactly your specialty, so these blueprints were even more confusing to you than those of the Core. Your frustration was forgotten, though, as soon as you found a note written in wingdings at the top right corner of the page;
"ENTRY NUMBER EIGHT
I HAVE A PLAN
TO BUILD MY OWN ASSISTANTS
THEY WILL BE MADE FROM MY OWN FLESH
SO AS TO INSURE THEIR INTELLIGENCE
I SUPPOSE
THIS WOULD MAKE THEM MY CHILDREN
IN A SENSE
ASGORE HAS TWO CHILDREN
THEY SEEM TO TAKE CARE OF EACH OTHER
PERHAPS I SHOULD MAKE TWO
I JUST CANNOT STAND ANOTHER MOMENT WITH THESE FOOLS"
Your magic pumped wildly through your bones as you read and reread the entry. This was the missing piece you'd sought after ever since Frisk had led you to number 9.
Finally, finally, there was confirmation that Gaster was your father. Or, well, your monster half's father. Because who else could he be talking about, other than Sans and Papyrus? "Made from my own flesh"... what, exactly, did that mean? As a skeleton, Gaster didn't have flesh, technically speaking. It was not something you usually thought about, but how did skeletons reproduce? As a skeleton yourself, you should've probably known that already, but it had never interested Sans.
And then, there was the comparison to Asgore's kids. Had Sans and Papyrus really been modeled after Chara and Asriel? This, plus the next chronological entry, seemed to suggest that. You knew that the whole tragic situation between those two kids occurred shortly before Sans' memory began, so perhaps you should've made the connection earlier. But Sans and Papyrus hadn't turned out anything like those two…
So why were you so unnerved?
Whatever. Your monster half and your brother must be more like Gaster than anyone, seeing how he was their sole parent. They had to have received all of their inborn traits from him. Plus, Gaster's plan had been to have his sons working beside him. Sans and Papyrus must've spent a lot of time with him, if that was the case. Though, it did raise the question of why your brother wasn't in any of those old photographs of Gaster's… perhaps those family photos had just been lost to time.
After sitting on the floor for an indeterminant amount of time while you sifted through blueprints, your bones were beginning to ache. You gave up on trying to decipher the rest of the soul blueprints; you had little hope of ever understanding them fully, and you now knew what they were for, anyway. You didn't need to know the gritty details. You put the one containing the new entry into your dimensional box but, regretfully, you couldn't save all of them in the same way. There was simply not enough room in your phone if you wanted to leave space for entries you still had yet to find.
You scooped up the blueprints which had to do with the layout of the Core, but left the rest behind. They were too bulky to carry in your arms while you explored, and, if you took them with you, you were afraid you would accidentally set them on fire by way of lasers. You would just have to come looking for them again when this was all over, if you wanted to return them to Alphys.
Thus began an endless quest to find the remaining entries. You started out with a method; using the blueprints to more effectively navigate the Core. At first, it was an effective strategy. You found Entry 13 only because you identified the room it was in as being particularly important to the function of the Core, and had spent extra time searching it. You found the piece of paper folded up in a tiny triangle, wedged in between two lasers.
After this, however, the blueprints became less and less useful. The more time you spent in the Core, the less sense it made to you. You were finding rooms which weren't even on the blueprints at all, much less in the correct location. It seemed like the Core was constructing its own rooms, or combining rooms to form odd, non-functioning amalgamations. Eventually, you grew tired of dragging the blueprints around, and left them behind in a relatively safe, brightly lit room. You knew you had only a slim chance of ever seeing them again, but they were rather useless now, anyway. Anything that didn't have an entry written on it was of little concern to you.
You were in the Core for so long that you were forced to stop and sleep several times. Despite this, you never grew hungry or thirsty; physical needs became meaningless this deep into the Core. The thought crossed your mind that you could very well be doomed to wander these halls forever, unable to die unless you chose to end yourself with a laser or in a pit of fire.
It didn't bother you as much as it probably should have. Your two halves would no doubt find it terrifying to be in this situation, but, luckily, they never appeared. It was radio silence in your head, with nothing to fill it aside from your own thoughts. And you were perfectly content with being lost in the fascinating ruins of this machine. Every wire and square of tile had been designed by Gaster, and you never felt closer to him than you did now. As illogical as it may sound given the machine's failure, you trusted this place to take care of you.
Sure enough, your trust had been well-placed. Not only did you eventually find entries 11 and 16, but the Core spit you back out at its entrance right after you'd found the last one. You were still missing numbers 1, 10, and 15, but you were starting to think that they may not be in the Core. It wasn't logical, but you felt like the fact that you'd come across the exit right after finding Entry 16 was no coincidence. You hesitated to call it a sign, which would imply that the Core itself was some kind of higher power... but something had to have been going on, one way or another.
Before you left the Core, you took out the three entries you'd found and read them over again. You felt like you were waking up from a dream, and had to remind yourself of what the journal entries said;
"ENTRY NUMBER ELEVEN
THE CORE IS BECOMING MORE DANGEROUS
EVERY DAY IT GETS HOTTER
AND THE WORMHOLES TETHERING IT TO THE PHYSICAL REALM
HAVE BEGUN TO DISAPPEAR
ASGORE HAS ASKED ME FOR A REPORT
ON WHAT WOULD HAPPEN IF IT WERE TO FAIL
TRUTHFULLY
I DO NOT KNOW
AND I DO NOT INTEND TO FIND OUT"
Right. That one didn't tell you much of anything that you hadn't already figured out from the blueprints. Gaster must have been pretty confident in himself if he thought failure was so unlikely that he hadn't installed any safety measures. Rather foolish, in retrospect.
You moved on to the shortest entry you'd found yet;
"ENTRY NUMBER THIRTEEN
I HAVE FIRED ALL OF MY STAFF
MOST OF THEM HAVE ALREADY QUIT ANYWAY
I DO NOT NEED THEM"
You thought you knew, now, why Asgore had pulled Gaster's funding. You doubted he'd taken it very well when Gaster dismissed all of the people the King had assigned to him.
You wondered, though… did Sans and Papyrus count as "staff"? Or had they still worked for Gaster until the bitter end? As far as you knew from the entries you had, Gaster made no mention of either of his sons after their creation, so you were left to wonder.
Lastly, your gaze slid to what you were convinced was the last entry you were ever going to find in the Core;
"ENTRY NUMBER SIXTEEN
INTERDIMENSIONAL FLUX HAS BEEN REACHED
PHOTON READINGS MAXIMUM
IT IS DONE
I WILL USE MYSELF AS A TEST SUBJECT
BUT I BELIEVE I HAVE FINALLY FREED US ALL"
Your chest ached at Gaster's final words. The Core had been functioning as intended right up until the final moment of truth. Your father thought he'd figured it out, when the only thing he'd succeeded in was erasing himself from existence. If he was still alive and sentient, you could only imagine how that last-minute failure haunted him.
Something about that entry struck a chord in your mind. It was painfully familiar, and you were sure it had something to do with the forgotten Entry 17. It annoyed you more than ever that you couldn't remember it and, to make matters worse, you had no more leads. While the entries you'd found were certainly interesting, they did not lead you to Gaster. You'd gained nothing of substance from this endeavor.
You sighed heavily before storing the entries back in your phone where they belonged. With that done, you continued forward, unsure how to continue.
The sight of Mettaton's hotel was jarring after having been lost in the Core for so long. You had no idea what day or time it was, aside from that it was as dark as when you'd entered the labyrinth. There was practically nobody in the hotel; there wasn't even a receptionist at the front desk. You hesitated in the lobby, then walked over to the burger emporium.
"Welcome to MTT-Brand Burger Emporium, home of the Glamburger. Sparkle up your…" Burgerpants' eyes appeared glazed-over, not truly seeing who was standing in front of him until he was almost through with his standard welcome speech. His eyes widened before he raised one brow in suspicion. "Hey, I know you… you were on the field trip, right?" Before you could speak, he snapped his fingers in realization. "Yeah, yeah… and you're that weirdo who walked through here with all those papers last week. I knew I recognized you from somewhere!"
"Yes." You replied simply. Burgerpants didn't seem deterred by your shortness of tone.
"Man, you really messed up that one human. That was WILD. I am never going on one of those trips again, let me tell you. I'll work the night shift everyday before I agree to THAT again!" You leaned on the counter, arms crossed, and tapped one talon on its surface as you listened to his mundane rambling. You still felt like you were in the twilight zone after that adventure through the Core, which had, apparently, been a week long. You were skeptical of that, since it sure hadn't felt like that much time had passed. "Mostly because of those, uh, helicopter things. And the humans were kinda freaky when they were all grouped together like that, too. Can you believe how they all look exactly the same? It's kinda creepy. Hey, are you okay, buddy?" He must've noticed you'd zoned out, and was looking at you with an odd expression.
"What time is it?" You asked in a quiet murmur. You were well aware that you were acting strangely, but just didn't care enough to put on a mask.
"Uh, it's like… two in the morning. Can you believe Mettaton's making me work this late? Even the receptionist got to go home. I think it's punishment for something, but I can't figure out what… hey, where're you going?" You walked out of the shop unceremoniously, too lost in your own mind to spare Burgerpants any more than a passing thought.
You had… an idea. It was an objectively bad idea, if you were to ask your two halves. But they'd screwed things up so much in the past, so what did they know? And, if you were starting to consider it, then at least one of them had to be okay with it too... right?
You were going to start up the game again. Just thinking it made you taste bile in the back of your nonexistent throat, but how else were you ever going to read Entry 17? There was no trace of the game left on the internet; no human remembered its existence, let alone the existence of a secret message in the game's code. You were resigned to the fact that you weren't about to suddenly have an epiphany and remember what the entry said. But maybe, if you could just find this one piece of the puzzle, you would finally be able to see the full picture. There were a few other entries you had yet to find, but this was the only one whose location you knew. And it was looking like 17 really was the last one… it had to be important.
I won't have to reset or reload anything… it's just a matter of changing the room number in the game files. You reasoned with yourself when, really, you'd already made up your mind. You took a few, rapid shortcuts until you were in your house.
It was empty, silent, and dark, as you would expect it to be at two in the morning. There was no one else in the house; you knew this, and yet you still tried to stay as quiet as possible. You moved from the spare room, to the living room, to your room... your bare, bony feet clicking softly on the hardwood floor as you went. You felt an unexpected fondness as your gaze swept over the dark bedroom. Despite your unwillingness to call this place "home" at first, it had become just that. You were glad to be back, if only for a moment.
The bottom dresser drawer creaked as you opened it, revealing nothing but your laptop inside. You removed it with care bordering on reverence. The plastic cover on your bed made an obnoxious crinkling sound as you sat on it. You took a deep breath before flicking the computer open, flooding the room with bright, artificial light.
You got right down to business and went straight for the Undertale files. Using the knowledge you'd inherited from your human half, you found what you were looking for. There were two files that you had to change; and file 0. You opened up the .ini file and…
Well, there was one crucial piece of information you were missing. What was the room number? You remembered that it was in the 200's, but beyond that, you had no clue. You let out a long-suffering sigh and started guessing, starting from room 201.
Your first guess took you to the Core. You figured that was far too low, and upped the anty to 270. That room, as it turned out, didn't even exist in the game. Instead, you got an image of a dancing dog and some upbeat music that was wildly inappropriate for the somber mood of the situation you were in. You snorted, and picked a lower guess.
Altering the game files grew less and less scary the more you did it. Nothing changed in real life as far as you could tell. After all, all you were doing was making guesses and opening the game to take a peek at what room you showed up in. There was no harm in that… at least, none that you could conceive.
Eventually, after guessing incorrectly a few times and ending up in various rooms in the true lab, you got it right. Lucky number 264 took you to a black screen, where shaky, wingdings font began to show up on screen accompanied by an eerie sound;
"ENTRY NUMBER SEVENTEEN
DARK DARKER YET DARKER
THE DARKNESS KEEPS GROWING
THE SHADOWS CUTTING DEEPER
PHOTON READINGS NEGATIVE
THIS NEXT EXPERIMENT
SEEMS
VERY
VERY
INTERESTING
WHAT DO YOU TWO THINK?"
The game suddenly closed itself, and you were left staring at your desktop image. "This next experiment"... this entry was found in the game. Did Gaster have something to do with…?
"What do you two think?"
You let out a full-body shudder as your breath caught in your throat. You knew… you knew what you had to do to talk to Gaster. It was so obvious, you were stunned that you hadn't thought of it before. Or, maybe you had, but your strong aversion to changing the files of the game had kept the thought from ever even reaching the surface.
You were more frustrated than ever with how slow your claws were at operating a trackpad as you opened up the game's files again. With shaky hands, you set the "fun" value to 66.
There was no way you were going to have this interaction through the game. You were going to go there… in person.
You saved the file at least five times before closing your laptop, shooting off of the bed with far more nervous energy than you knew what to do with. If everything worked like you thought it did, and what happened in the game still determined what happened in the Underground… then there should be a grey door waiting for you in Waterfall.
"What do you two think?"
You were ready.
