They set out soon after, walking up to the River person. Sans is a little sluggish, apparently still recovering from whatever his brother did to him. When they arrive at the little alcove where the River person usually is, however, they're gone. A tiny note lies on the ground. Sans picks it up.
"hm… 'la la la, river running the wrong way. taking my vacation now, lo lo lo.' and that's all it says."
"I GUESS EVEN RIVER PEOPLE GET VACATIONS," Papyrus muses.
Sans sighs. "y'know, i normally couldn't get mad at someone for slacking off, but in this case…"
Undyne frowns. "Sans, just do your weird shortcut thing, we don't have time to waste if you want to catch up to Gaster."
"right," Sans says, rubbing his left temple. "i'll try." He seems to focus for a minute, then gasps for air. "h- hold on…" He concentrates deeply, but nothing happens. "this isn't working… maybe i can see when the river current will change." He tries to focus again, but gives up after a minute. "i… i don't think i can see anything either…"
"YOU'VE GONE BLIND? YOU MUST'VE HIT YOUR HEAD REALLY HARD!"
"no… no, i just can't… concentrate on it. i can't use my magic," Sans says, looking at his left hand. "i can't use any of it… it's just gone."
"Your brother probably took it from you," Undyne says.
"He did get a blue eye right afterwards," Flowey points out. Sans frowns, looking disturbed by that idea. "So… how are we getting back to The Core without the boat?"
Everyone is silent for a moment until Papyrus speaks up. "WELL, I DID MAKE A RAFT AS PART OF A PUZZLE ONCE."
A few minutes later, they're all floating down the river leading to Hotland. Undyne and Papyrus are taking turns rowing, and between the two of them they're actually getting them there at a decent speed, especially once the river's current shifts back to normal. Sans, still exhausted, is lying on his back, occasionally snapping phalanges, trying to get a blue spark to appear. So far, he's been utterly unsuccessful.
Flowey looks to Frisk. "Hey did I ever tell you about when Chara told me they were a pirate?" Frisk shakes their head. "Okay so… basically they said they used to find buried treasure and feed people to sharks. …Mostly feed people to sharks. And they had a sword so sharp it could cut a ship in two."
"That's not real, is it?" Undyne asks.
Flowey looks a little embarrassed. "Well… no, but I believed them for a while. I was still pretty little. I even believed it when he said my dad's trident was stolen from their old rival- Poseidon- I think he might've been some sort of dinosaur."
Recolection flashes in Undyne's eyes. "Wait… did you say trident?"
Flowey seems to realize his mistake. "I uh… meant pitchfork. Chara just said it was a trident to make it sound cooler."
"You're really not a good liar you know," Undyne tells him. Flowey looks away sheepishly. "What's your dad's name anyway?"
"Uh.. uh… Erogsa," he says quickly. I can't even help but feel frustrated by how transparent he can be sometimes. One would think years worth of villainy would turn him into a decent liar, but no.
"WOW, YOUR DAD HAS THE SAME NAME AS KING ASGORE, JUST BACKWARDS," Papyrus says.
"Nice job spotting that," Undyne says.
"THANKS, I DO THE JUNIOR JUMBLE A LOT."
Flowey looks away from them. "Huh… uh… some coincidence, right?"
"Oh yeah, definitely," Undyne says with a little smirk.
Meanwhile Sans looks up at a crystal as they float down the river. "hm…"
"SANS, YOU HAVE A WEIRD FAR OFF LOOK, ARE YOU SURE YOU DON'T HAVE A CONCUSSION?" Papyrus asks.
"yeah, i'm sure," Sans says quickly. "i was just… thinking, i guess."
"About crystals?" Undyne asks, distracted from her interrogation of Flowey.
"well… yeah, sort of," Sans admits. "w.d. used to take me through here. he'd point out the crystals and ask me if i knew how they work. 'magic, right?' i'd say, and then he'd ask me if i knew how magic worked. heh, lots and lots of talk about how the crystals convert magical energy to light energy, back and forth… it was fun."
"IT… SOUNDS GREAT?" Papyrus says uncertainly.
Sans smiles a little. "well you never found it very interesting."
"OH! THANK GOODNESS," he replies. "HEY SANS, WHAT IS THIS OTHER ME LIKE ANYWAY?"
"oh, well... uh, you were in the royal guard, and you-"
"I WHAT?" Papyrus interupts.
Sans seems amused. "yeah, bro, it was sort of cool. w.d. might've pulled a few connections, he was still proud of you though, heh..."
Papyrus grins, almost looking jealous of himself. "I BET I WAS SO... POPULAR!"
"yeah, but you kinda hated the job," Sans says.
Papyrus stares. "HOW COULD I POSSIBLY HATE IT? I'VE ALWAYS WANTED TO BE IN THE GUARD..."
"you just hated being mean to anyone."
"Sounds just like Papyrus," Undyne says.
"MAYBE..."
"I always kinda thought you'd be happier in a different line of work," she says. He taps his mandible thinking about that.
Flowey looks at the glowing gems around him. "So, he liked these weird crystals?" he asks. "Gaster, I mean..."
Sans nods. "definitely… we spent a lot of time here. and he'd tell me, 'look, you see the ones embedded in the cavern ceiling? a lot of monsters use those to make wishes.' and i'd say, 'well what do you wish for?' and he said… 'me? well… i'd like to see the sun some day.' i asked what that was, and he told me it was a star that was so close to us it looked huge for half of a day, whenever we could see it. and it was so bright that even when we were faced away from it, it would often reflect back off of other planets and off of a big rock in the sky."
"YOU ALWAYS DID LIKE OUTER SPACEY STUFF. BUT SUPER CLOSE STARS? GIANT ROCKS IN THE SKY? THAT SOUNDS FAKE," Papyrus says.
"No, those are real," Alphys says. "The humans are able to see them every day, just ask Frisk."
"FRISK, IS THERE REALLY A GIANT ROCK IN THE SKY?"
*Yes. No.
"OH, WOW, THAT'S SORT OF COOL."
"yeah," Sans says. "course then he'd start talking about how the sun is different from the false stars here… the sun uses nuclear power and emits radiation, while the crystals use magic to emit radiation in the form of light.. and then he gets this idea. he said 'you know, if magic can become light, how hard would it be to turn light into magic?' but we don't have much light down here… a radiation we do have is lots and lots of heat over in hotland."
"And… that's how he got inspiration for the Core?" Alphys asks.
"yep," Sans says.
"Hmm," Undyne says. "You know, he kind of sounds like… a nerd."
"how insightful, thanks for that input," Sans says. "well anyway he is, but… i mean, in spite of everything, i don't think he has it in him to hurt anyone… you know?"
"He took your weird powers," Flowey points out.
"yeah, and i don't know how he did that… but still." It's almost touching seeing the extent Sans wants to believe in his brother. Still… once I find Gaster, I'm going to murder that piece of garbage skeleton even if the only weapon Frisk has managed to find in this whole run of the timeline is a little toy knife.
It's a while before they arrive at Hotland, and even then after that, they still have to get to the elevator and ride all the way up. Undyne is holding her head, looking like a fish out of water. "We need to hurry… I hate this place so much."
"You know this might be the last calm before the storm," Flowey points out.
"There won't be a storm," Sans says firmly. "at least… i really hope their won't be."
They go up through the MTT resort, into the core itself. This is nearly the end, I suppose… time to find Gaster. As they go through the levels of the MTT resort, they have to stop suddenly when they reach a dead end. Alphys walks in front of them, going to a computer terminal. "This isn't s- supposed to be here," she says. "Here, I can override it so this passage way opens up." After a few moments of typing, the screen flashes red. She taps a few keys and frowns.
"What's wrong?" Undyne asks.
"It's just this c- computer… I've been locked out? Uh…. Maybe he reprogramed them."
"He must know we're coming," Flowey says.
After a few minutes of wandering, they walk into a room that is mostly a large, empty space. A bridge spans the gap between the room before and the next. At the center of the bridge Gaster stands, looking up at the ceiling and not yet reacting to their presence. Frisk approaches cautiously. Without even looking at them, Gaster speaks. "You're here now… are even you planning on stopping me, brother?"
"What did he just say?" Undyne asks.
Sans translates quickly before looking back towards Gaster. "that depends, w.d. what are you gonna do?"
"What am I going to do…" he repeats. "Hm... You must realize, Sans, that this world," Gaster says, looking out over the core and gesturing broadly, "is broken. This timeline is wrong… its events are out of place. My erasure quite possibly triggered the fracturing of this timeline. I must be the one to fix it."
"fix it?" Sans asks after translating what he said. Everyone around him is growing anxious. Whatever Gaster has planned, I doubt it will be good.
"Yes," he continues. "You see, there is a fundamental anomaly in this timeline – a crack that allows those with slight control over the universe to impose their will over it. Resetting, redoing, shaping the events to their will, over and over." He turns his gaze towards Frisk and Flowey. "Saving… resetting… you two have done so much more damage than you even realize. You think that you're helping… don't you?" He throws his head back, looking at the mechanisms of the core. "All you've done is deepen the cracks. Tell me… did you really ever expect this to be the last time you go through these motions? Did you expect to simply be done with this world once you fix whatever mistake you perceived to begin with?" He strides towards them and Frisk walks backwards in fear. "No… impossible. Your very existence is tethered to these resets. A sickness has crept into you, little fallen child. A compulsion you have no chance of breaking. You, yourself, are now just as much of an anomaly as the flaws in the universe that give you your power."
"You're wrong," Flowey says. "It wasn't ever Frisk resetting constantly… they just got caught up in this."
Gaster tilts his head. "I'm aware of their… situation. But nonetheless, they are the avatar that allows the fallen child into this world. I do not plan to kill them, don't worry. They are powerless to stop me now anyway. An agreement was reached." He lifts his right hand, cloaked in red magic. "I asked only for DETERMINATION. I never said how much. But I don't expect that your little "Chara" has much strength over them now."
In a panic, I look at Frisk's health, now maxed out at ten. I try to move them… nothing at all, even though they aren't guarding against it. He tricked me… and now I'm powerless.
Gaster looks around at the others. "They will be erased along with the other anomalies of this timeline. Which is… everyone changed by the events that were altered."
"w.d. you can't do that!" Sans objects, not even bothering to translate what he said to the others.
"And why not," Gaster asks. "You must know these are not the people you grew up with, Sans. Even your brother there…" He points to Papyrus. "That is not the Papyrus you knew. Not the Papyrus that we knew. He is not our family." Papyrus looks to Sans in confusion and uncertainty.
"yes he is!" Sans says angrily, not even considering the alternative. "he's just as much my brother as you are! and just because everyone here isn't from the original timeline doesn't mean they aren't still monsters! these are lives you're talking about taking, w.d. not some simple thing you can fix. how's doing what you think you're going to do any different from what you said frisk and flowey did? huh?"
"Because I will be resetting the timeline to how it should be, not just what pleases me most. You're letting your judgment be clouded by false sentiment, Sans. Let me relieve you of that."
With a flick of his right wrist, Papyrus is thrown sideways, hurtling off the bridge.
"NO!" Sans gasps, lifting his hand and trying to use his power to pull him back. It's only a split second before he remembers, and the utter horror of the situation can be seen through his eyes. Undyne runs to the edge, but can't grab him.
Flowey acts quickly, sending a few bullets zipping through the air. They hit Papyrus in his armor, pushing him just high enough back up that Undyne can grab onto his leg. She and Sans hoist him up, and though he looks like he's in shock and his armor is severely dented, he's alive.
Gaster looks unamused as he walks towards Flowey. "The child, the lesser skeleton, the warrior, the scientist, even Sans… they're no threat to me at all. You… on the other hand…" Gaster stops and looks at Flowey closely. "Hm… what even are you? Such power to cause so many changes across time-space, and yet you are a simple houseplant?" His blue eye suddenly glows sharply, much the same way that Sans's did. "Or a being without a soul? How very… very… interesting."
Flowey is pulled suddenly away from the others, a blue field of magic surrounding him. "What are you doing?" he asks fearfully.
Gaster seems to be ignoring him, talking to himself. "No soul… then his life shouldn't even be possible. And yet, he has autonomy… he has sentience… this could be exactly what I need. But who exactly are you…" His red eye glows brightly and he waves his hand.
Suddenly, surrounding all of them are what look to be moments of his life… Asriel playing through a garden… Holding a child up with his shoulder and helping them walk… collapsing back at the royal palace after his short venture to the surface… a golden flower growing where he fell, before being plucked out of the ground by Alphys.
"I see," Gaster says, looking at him. "The young prince Asriel… something seemed familiar about you. But that matters little… you may have once represented a hope for monsters coexisting with humans, but now you will live up to that promise by destroying that which separates us."
"Let. Me. Go!" Flowey says, struggling.
"No," Gaster replies. He has to duck as a spear suddenly swooshes past his face. "Ah… so that's how it'll be." He moves Flowey back behind him and rubs his hands together, blue and red sparks flying from them.
Undyne throws another spear at him, fury in her eye. He deflects the hit easily, using the blue and red energy to tear metal panels from the walls and use them as shields before throwing them. Undyne yells and jumps, landing agilely on top of one before jumping to the next to get another stab in. He throws another metal sheet, but she lands just as easily on it.
Sans and Papyrus are running towards Gaster, and Papyrus tosses a few bones his way. With surprising agility, Gaster evades them. Sans sneaks in one extra hit and it nearly hits Gaster before he waves a hand, disintegrating it.
"papyrus, blue!" Sans says quickly.
"RIGHT!" he replies, launching a blue attack. Gaster simply pulls Undyne into the way of it, and she sinks to the floor, weighed by the sudden increase in gravity. "SORRY UNDYNE!"
She tries to stab at Gaster again, but the sudden slowness allows him to easily dodge her attack. Alphys picks up a piece of metal from the ground and throws it, hitting them in the side of the skull. All it seems to do is anger him however and he rushes towards her. "Was replacing me not enough, Alphys?" he asks. She walks backwards in fear.
Undyne takes the opportunity to stab at him from behind. "Don't you dare hurt her!" she shouts.
It only narrowly misses as Gaster vanishes and reappears on the other side of the room. "Predictable… how far the royal guard has fallen in this timeline."
With his back turned to them, Frisk grabs Flowey, holding on tightly. Gaster looks back and waves a hand, shaking both Flowey and Frisk vigorously. Frisk is only able to hold on for a minute before they're sent crashing out of the room and into a wall. Gaster wastes no time with the others, throwing them into the room in front of him.
"Now then," he says, "If you're all quite done, I have a timeline to save." He turns and walks away from them with Flowey in tow.
In spite of being hurt from being thrown into a wall, Frisk quickly pushes themself up and chases after them. Gaster turns and his blue eye flashes, unceremoniously sending Frisk flying sideways, off the walkway.
"Frisk, NO!" Flowey cries out. "Frisk! Frisk!" But their voice is growing quieter and quieter as Gaster walks away with him.
Papyrus is the first to scramble up, still listening to Flowey's voice. "FRISK? …OH NO!" He spots them dangling from the edge, and quickly pulls them up and hugs them tightly. "OKAY, YOU'RE ALRIGHT NOW… HEY WHERE ARE YOU GOING?" he asks as Frisk struggles to pull themself away from him. Frisk isn't listening, they're already trying to chase after Flowey. "HEY STAY WITH US, FRISK, DON'T LEAVE."
Sans and Undyne are catching up to them.
"Did you guys see all those weird visions?" Undyne asks. Sans nods, but says nothing else. They don't have time to discuss it.
Frisk is still moving forward. They look around for any sign of Flowey or Gaster but they both seem to be gone without a trace.
"stay determined," Sans says quietly, pulling them along, towards a point he seems certain Gaster could be going to. "we need to find him, and soon. we have a timeline to save."
AN: Two more chapters. I think i'll go ahead and upload them both at the same time some time this weekend, so be on the lookout for the conclusion. Also, I added a few extra lines of dialogue in this that aren't in the ao3 version of the story so hey, that's the bonus of reading it on here I guess? You don't get cool fonts, but you do get a few new lines about the other timeline's papyrus.