It had only been a month or two since monsters have left the underground, and the CORE already looked so different.
Sans adjusted himself to the smoldering heat, tempting fate with every step he took on the crumbling platform. The CORE was now inactive, the last remaining bursts of heat slowly melting away at the grand machine. Every so often, a brief flash of blue or yellow would flicker at the bottom, as if the machine refused to die, but the brief bursts were offset by the orange glow of the heat below. He stopped as he approached the left edge of a long corridor, barred by loose rails. This was where Gaster fell. If his vague memory weren't enough to go by, the data readings sure were.
Sans pulled out a small cubical device, watching the readings start to spin out of control. The temperature bounced up and down rapidly, the time fluctuations getting worse and worse the closer he moved to the edge. The FUN value was shifting rapidly near this small section, each panel changing dimensions, each so similar that nothing seemed to be wrong at a glance. Even in his bones, Sans could feel his magic losing it's form and control, his magic growing chaotic near this site. The stability of time-space here was weak. Good, it meant he was close.
Sans pulled out his phone, and tapped in Alphys' number.
Alphys shoved another piece of popcorn into her mouth, watching the screen, which projected an anime about magical fighting princesses. Next to her was Undyne, who was watching with intent. Suddenly, Alphys' phone rang, playing the theme song to Mew Mew Kissy Cutie. "Oops!" Said Alphys. "Hey, Undyne, can you pause the show, I-I'll be back in a second."
"Who calls at 11pm!?" Undyne growled, but paused the show anyways.
Alphys picked up the phone. "H-hey, who is it?" She whispered into the phone.
"it's sans. i'm at the spot, do you have the machine ready?" He said,
"O-oh, I didn't think you would be that quick. Hey, um, can you wait for ten minutes, you know me and Undyne watch anime on Sunday nights. Just this one episode, I p-promise, it'll only be like fifteen minutes, please I just-"
"hey it's ok, it's no rush. i could always use extra time for nothing. time sent doin' nothing is my favorite time." Normally, that would be true. Right now though, that was a lie, Sans couldn't wait to get the machine on. He had been working on it for so long, and finally it was time to get some accurate readings. Time to find Gaster.
"Ok, sorry, I'll go get the machine running and call you back, ok?"
"ok, but don't wait too long, you wouldn't want me falling asleep right into the core. by the way, remember, if you tell a single soul about this, i'll you into a fossil."
Alphys ended the call with a nervous gulp, walking back into the room.
"Who was it?" Said Undyne, rather grumpily.
"Just Sans." Replied Alphys. "N-nothing important, just another p-prank call."
"Another prank call? Ugh, I swear, sometimes I just want to.." Said Undyne, rubbing her temples. "Let's just get back to the show."
Sans could almost remember seeing Gaster here, prepared to harness the CORE's power in an attempt to shatter the barrier. A machine that could remove the barrier from existence, to free monsters from the terrible prison that encased us all.
But, with one false move, one slip into the CORE, Gaster got not only himself erased, but every single copy of him in every timeline. Even memories of him seemed to fade, all but to Sans, who rediscovered Gaster in his dreams of The Void. The Void was always inky black, like light itself was being absorbed, with nothing in sight but sometimes Gaster would be in a grey, featureless room. It was his home in The Void, a single piece of creation in the endless emptiness.
After several failed attempts at getting Gaster back, Sans had discovered that The Void was outside of any of the timelines, only briefly and rarely accessible through a few timelines, with the right FUN value. FUN was an acronym. It stood for Fluctuating Universal Number. Every timeline had one, and it always changed when the human reset. Every reset was awoken from like a dream, but between those brief periods, when Sans was truly asleep and not thrown into the next reset, Sans dreamt of Gaster, and spoke to him. With the help of Alphys and the human themselves, the Timeline Machine was almost repaired. A machine that could displace someone from one timeline or plane, to another.
After many dreams, Sans and Gaster formulated a plan to find Gaster in this splintered timeline, and restore him to reality. Even in those dreams it seemed ridiculous, but now, he felt so close to discovering Gaster's whereabouts. Just as long as nobody gets in the way, every should be-
Sans turned around, hearing the noise of footsteps. His eye-sockets went blank, his shoulders tensing up. The footsteps were heavy and fast, like somebody running at full speed. Sans quickly stuffed the small cubic device into his hoodie, and ran to the entrance of the short corridor. If it were one of the Gaster followers, he would surely find himself in a fight, or worse yet, if The Void itself somehow sensed his plan.
Sans' left eye started glowing a bright cobalt, as he prepared a rapid blue attack, only to stop when he was not attacked, but hugged.
"BROTHER! WHAT ARE YOU DOING HERE!?" Said Papyrus, picking up Sans in a hug before putting him back down. Papyrus was wearing a loose orange sweater, with his favourite red scarf still there, stuffed into the neck of the sweater (Papyrus' strong suit was never fashion, pun fully intended) , making his appearance at the CORE all the more surprising. He was definitely not dressed for it. He probably ran through the entire underground to get here.
"i should be asking the same thing." Said Sans. With everybody gone, the underground had become twice as dangerous, with puzzles laying unattended and Flowey still underground. God knows what Sans would do if that flower hurt Papyrus. Nevermind that, how did Papyrus even know he was in the underground?
"I HEARD FROM THE HUMAN THAT YOU CAME HERE FOR... "RESEARCH"? ARE YOU TRYING TO FIGURE OUT THE BEST WAY TO COOK YOUR FOOD, BECAUSE I CAN ASSURE YOU THAT A STOVE IS MUCH BETTER THAN AN ENDLESS PIT FULL OF SEARING HEAT!"
"heh, not exactly." Sans considered for a second to tell Papyrus about Gaster, but stopped. No, Papyrus didn't need to know until the time came to return Gaster. Sans would sound crazy, telling Papyrus that they had a father that he was trapped between dimensions.
"WHAT ARE YOU HERE FOR THEN?! CAN I HELP!?"
"paps, it would be best if you went back home. frisk needs you." Sans made up something quick on the spot, hoping Papyrus would return to the surface. To his surprise, Papyrus only gripped his shoulder in response, shivering ever-so-slightly. "what's the matter?"
"THIS PLACE GIVES ME A BAD FEELING. LIKE SOMETHING BAD'S GOING TO HAPPEN HERE. IF I'M LEAVING, I WANT YOU TO COME WITH ME." Papyrus seemed uncharastically quiet, though his voice still very loud compared to Sans'. It was almost like Papyrus could recall what happened here, yet Sans knew that it was impossible, given Gaster's wipe from existence.
Sans sighed. "ok, just give me a second." Sans took out the device, attaching it to the edge of the CORE's corridor, when he felt a presence looming nearby.
The presence was so familiar, nearly completely in sync with his own soul. The presence could be none other than Gaster, but why was he observing now? The cubical machine shook, as the CORE let out a mighty groan. The corridor had began to break down, the machine the final straw on it's crumbling spires. The rails snapped off as the ever-hungering fires of the CORE's pit consumed them.
Sans' leg slipped off the edge, catching him off-guard, but he had to attach the machine on. He could almost hear a distant distorted screaming, as if Gaster was trying to tell Sans to get away quickly. The risk is worth it, if it meant getting Gaster back. Bits and pieces of the corridor fell with their support, the cube machine with it. Quickly, Sans turned around to get on his feet and teleport away, but his other leg slipped off. Before he could fall, a bony arm grabbed him.
"SANS, WE NEED TO GET OUT OF HERE!" Papyrus ran to his brother, catching Sans before he could slip further.
"i'll be fine, just run away!" Said Sans. Sans caught his breath as Papyrus panted, trying to escape the CORE's collapse. Holding Sans quite visibly held him behind as he let out a huff. "i can teleport, papyrus, i'll be fine, just save yourself." The platform gave way under Papyrus and Sans, sending them falling towards the CORE.
Sans, panicked, sent a row of bones bursting out from what remained of the corridor, catching their fall just before they landed into the CORE. Blue and yellow flashed below like menacing jaws, and the distant heat was charring his bones. It was like Grillby on a bad day. Sans let out a sigh of relief, but Papyrus was quite visibly shaken. "SANS! OH MY GOSH! WE'RE GOING TO DIE! WHY ARE YOU EVEN HERE!?"
"well, if you want to get to the core of the issue.."
"THIS IS NO TIME FOR PUNS!" Yelled Papyrus, a mixture of confused, angry and scared. The bones were slipping, and San's had a hard time keeping focus on his magic.
"we don't have very much time, do we? i was hoping for more time to tell you the story. someone's lost here, and i was looking for them. i needed the machine to attach to the core to look for them, but now it's... gone." Sans looked below, the bone wall starting to crack open to reveal the void below.
"DID THEY FALL IN?" For how naive Papyrus usually was, he seemed to have a relatively good gut instinct going into this. D-did he know? Sans couldn't help but start to wonder.
"yes, but don't worry, we aren't going to. papyrus, grab onto me, and don't let go." Said Sans, conjuring up all his magic. There was one last shot to get out of here. Teleportation.
Focusing on his soul and it's attunement to Gaster, he tried to displace himself away. Papyrus grabbed onto Sans, holding tightly, his gloved hands digging into Sans' hoodie. Blue magic fizzed around them, trying to move, but it chaotically coiled around the surrounding area, draining Sans far more than it should. His magic was vile and uncontrolled, much different than the usual precision of it's might.
The space here was warped by The Void. The magic was being absorbed by it's instability, leaving the spell distorted. It was as if something grabbed his magic and tried to pull it from his body, tearing it into bits. Was this what it was like when Gaster fell? Magic torn to shreds from inside out? Sans couldn't help but wonder as the spell failed.
"something's not right. it's not working." Sans could hear his own voice fading out as his magic darted in a chaotic manner, displacing him several times in several differing spots, glitching back and forth as the CORE drew nearer. The distortion of time-space here was too great. Sans could feel his arms drop in defeat, only to be held back up again by Papyrus, gripping his hands tightly. Guilt hung in his imaginary stomach like a stone. He failed Papyrus, and now they both were going to die, or worse.
They were in freefall, the corridor crumbling beside them, the orange heat consuming the pillars like a wolf might a sheep. The CORE was melting into itself, blue and yellow flashes bursting quicker and quicker. The time-space grew distorted, making what was seconds feel like minutes spent in a hopeless fall. The blazing chaos of the CORE came closer and closer, both of the skeletons feeling them forms and magic starting to lose their stability. Sans hands detached from Papyrus', but the taller skeleton was quick to latch back on.
"DON'T LET GO SANS, I-I'M SCARED."
"it's ok, i am too. i am too. "
The CORE's light devoured both Papyrus and Sans in it's searing glow.