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Timeline Cave In

Chapter Text

“Come on Chara, I finally figured out the piano puzzle!” Asriel shouted as he ran through waterfall.

“I’m comin’ Rei. Keep your bandana on.” Chara said as they slowly trudged behind him. On one hand Chara was doing this to annoy their brother, forcing him to stop running every few seconds to wait for them to catch up. But on the other. Chara spared a glance of the shoulder. Shifty was still following them. The slightly younger human has been trailing behind Chara and Asriel all day now. Chara turned their attention back to Asriel.

A mirror indeed ,” Chara thought. Shifty reminded Chara so much of when they first arrived underground. Curious and blank. At least after a few resets, Chara finally made a breakthrough and connected to the Dreemurr family. But Shifty, Chara still had no idea what caused Shifty to stop. Sure they could attribute it to killing them so many times when they tried to murder the whole undergound, but Chara wasn’t sure about that. They haven’t even loaded since they reset from that particular timeline. This was the longest timeline Shifty has done. Around three years Chara has been watching them, and they only got blank stares in return. They’ve basically only been talking to Asgore about engineering, and a few miners, but that was about it. Shifty hasn’t connected with anyone, they haven’t been living for the past few years so why. Did. They. Stop? 

“About time you started moving to catch up Chara.”

Chara paused in their walking, finding that, they indeed have been walking faster. They shook their head and forced their pace to slow down. “Well of course, I’d do anything for my little brother,” they said with a smirk.

Asriel pouted for a quick second before his lips curved up. “If anyone here is the little sibling it’s you Chara. I passed you last year.”

Chara looked up to give him a slight glare. He was right, but Chara would always have a leg up on that. “Fine then. I’d do anything for my baby brother.” Asriel puffed out his cheeks and continued down the path.

They finally made it to the piano room puzzle. Asriel ran from Chara to the piano and climbed on top. Chara’s eyes locked onto his feet on the wooden panel.

“Uh, Asriel? You sure that old thing can support your weight?” Chara asked. Their eyes flickered to Shifty, who was standing stockstill by the cave entrance. “ If he breaks it I could always just kill them to force a load .” Chara shook that very dark thought from their head.

“Hm?” Asriel looked over at Chara. “Oh, no it’s fine. I already tested it yesterday. Besides, I’ve got to wipe off the dust again.” Reaching as high as he could, Asriel wiped his furred hands against the stonework.. He had to get on his tiptoes to get the top of it, but when an audible creak groaned out, Asriel quickly went back to standing flat-footed against the wood. Once he was done he hopped down. Chara approached to inspect his work.

Asriel dusted his hands off. “Well, what do you think?”

Chara squinted. “Are those . . . music bars?”

Asriel nodded. “Yep! A couple days ago I noticed them carved into the stone, and I bet if you play it we can solve the puzzle and find the legendary artifact!”

Chara just stood a foot from the piano looking at the carvings. There was something off about them. The “font” was much different than other old stone carvings Underground. “Nice job Rei. Now if you can actually write those notes down for me, I can play this thing.”

“What, you can’t read it yourself?”

Chara stepped right up to the piano and experimentally pressed their fingers against the keys. The top stone wall was jutted out, forcing the carvings to be barely in front of Chara. “Well I could if you wrote them down, because my stupid human eyesight makes it hard to see from here, so unless you want me to play on stilts, I’ll need you to transcribe.” 

“Well I guess I have no choice but to help you then, since you simply don’t have the skill like a deity like me would have. It would be an easy matter for me to do such a thing.”

“Oh?” Chara asked with a smirk. “Then why don’t you, oh god of hyperdeath?”

Asriel looked off to the side. “Well, I could . . . if I knew how to play the piano.” Asriel walked over to the left wall and pulled out a piece of crumpled paper. “I didn’t think we’d need music sheets, so I’ll just have to draw the lines, sorry if they’re messy I- oh thanks newcomer!” 

Before Asriel could press the paper against the wall, Shifty pulled out a small piece of blank sheet music, only about three lines long. Asriel took it and pressed it flat against the wall.

“You know, at some point, I need to come up with a better nickname for you than “newcomer,” you’re not exactly a stranger after three years,” Asriel remarked while writing on the piece of paper. Shifty did not respond.

Don’t bother Rei, it’s not like they actually care about monsters anyway ,” Chara held back. “ They’re just waiting for whatever they want and then they’ll either leave or kill us. ” 

Before Chara could continue with their train of thought, Asriel slipped the piece of paper onto the piano. “There you go. Now that you’ve had the help of a deity Chara, there’s no way you won’t unlock the puzzle!”

“I’ll do my best bro.” And with that said, Chara began to play. The tune was simple; it started low rose to higher notes, and then jumped back to low. It took a couple of times for Chara to get the exact timing right, but when they did, the stone door opened by the back wall.

Asriel jumped up. “Yes! We did it! They’ll put our names in the history books! Let’s go!” he shouted before dashing into the room. 

Chara turned to get up and noticed something. Shifty was now about half a foot away from the piano, a bit too close for Chara’s comfort. Their facial expression was . . . different. “ Maybe nostalgic? ” Chara thought. And they were just staring at the piano. Chara carefully slid away from the frozen human, and entered the room.

The room was fairly small, maybe a little smaller than Chara’s bedroom. It was completely blank. The only thing of note was a pedestal by the back wall with a red orb resting on top. Chara walked up to besides Asriel as he stood in front of the pedestal, looking at it in wonder.

“Whatchya waiting for, bro? Grab it,” Chara said.

Asriel shook the stars out of his eyes he turned to Chara. “Why would I do that?” He asked while tilting his head. “We both got it, we should grab it together.” 

Chara wrapped their arm around Asriel in a one-armed hug. “Aw, thanks Rei.”

Asriel returned the gesture. “Of course Chara. I may have found the solution but you’re the one who actually solved it. I’m not going to steal credit from you.” When the two of them released each other, they both walked to the pedestal. Each of them stood on one side with their hands at the ready.

“On three, ready, Chara?” Asriel asked. “One. Two. Three!” Both of them reached their hands out and lifted the orb from underneath. “We did it!” Asriel cheered. Chara couldn’t help but smile. They were sure was at least as goofy as their brother’s.

“Oh, are you going to take a picture for this newcomer?” Asriel asked.

Chara froze, and slowly turned their head to see Shifty had their phone out. They pressed something. They dropped the device by the threshold, and bolted out of the room, back towards the hallway.

“Watch out Asriel!” Chara moved on instinct. They dove over the pedestal and covered the monster’s body with their own. They both hit the ground not a moment too soon as Chara heard a thunderous BOOM go off behind them. The room shook and rumbled. Something slammed into Chara’s back. And then again. Then again. But Chara refused to let the pain buckle them, they were determined to not let Asriel get crushed.

The ground continued to shake, the rubble shifting and slamming into Chara’s back and sides like dice in a yahtzee cup. After what felt like hours, it all stopped. Chara had no idea what was going on. All they knew was that there was a lot of weight on their back, and it was very, very dark. 

“R-rei, you good?” Chara asked, coughing up some blood. The silence after the question sunk into Chara.

“Yeah? I think so. What happened?” Asriel answered, after what was probably a few seconds.

Chara chuckled without warmth. “The human decided to bury us under this rubble. They were probably hoping to kill us with this than have to fight us head on.”

“But Chara,” Chara could hear the confusion in Asriel’s voice, “the newcomer wouldn’t do something like th-”

“Yes they would! I’m not just saying that because they’re human. I know what they’re really like!” Chara spilled out.

The terrifying silence came back. Chara counted ten breaths before Asriel said, “Okay Chara, I believe you.” Asriel paused again. “So, what now?” 

Chara tried to push the weight on their back. They almost collapsed from the pressure. “I have no idea,” they grunted out. 

“Oh, I know! I’ll use some magic,” Asriel said.

“Don’t Rei, the destruction would probably kill us both.”

“Calm down, I just was going to bring some light.”

“. . . oh, I guess that’s fine.”

Asriel snickered before Chara’ eyes were filled with light and colors. Once Chara’s eyes adjusted, they noticed Asriel chest was right below them. His hands were close together holding a star of shifting color. Looking up Chara had to withhold a gasp at his injured state. A few rocks and cuts were sprinkled across Asriel’s face. And judging by his expression, Chara was pretty sure they weren’t any better.

“Heh, are you pregnant Rei?” 


“You just have this glow about you.”

Asriel huffed. “Really Chara? Can you ever stop teasing me?”


“I thought so.” Asriel looked around. “Okay, so, on the plus side, we still have the legendary artifact.”

“Oh my god Rei, forget about that thing!”

“No! I don’t want us to get out of here with nothing to show! Once we do, Mom’ll heal us up, and then we’ll be heroes.”

That is, if we get out of here at all,” Chara thought. “Well, let’s first worry about getting out. Asriel, my phone’s in my left pocket. Try to fish it out and call Dad, he’s on speed dial. Just hit two.”

Asriel shifted the star to only be emitting from one hand and reached the other into Chara’s pocket. They yelped.

“What the-” Asriel began as he pulled something out from the pocket. A long winged green serpent was pulled out of Chara’s pocket, a space it definitely could not fit. Once out of confinement it slipped out of Asriel’s grasp and wrapped itself around the red orb. The next thing Chara knew, the artifact was gone, and the snake was slightly bigger. 

“Did you . . . did you just eat the legendary artifact?” Asriel asked.

“Uh . . . actually I think it absorbed it,” Chara pointed out. Before Asriel could respond, the serpent’s tail flicked his face. And then if flicked Chara’s. It’s tail then landed on Chara’s hand, and whipped back and forth between Asriel and Chara’s hands.

“What the heck is it doing?

“I . . . think it’s telling us to grab its tail?” Asriel said.

“I think so too. But I don’t think I can move my arms with all these ro-” Chara was cut off as the serpent’s tail slipped into their clenched fist, pushing through the space between the skin like thread through the eye of a needle. Asriel lifted his own paw and wrapped around the tail above Chara’s hand.

The serpent launched itself out from in between the siblings. Chara and Asriel were yanked from the crushing weight of rocks, directly into rubble wall. Even as Chara felt their face slam into the stone, they could tell it was giving way to them much easier than it should, almost like paper mache constructs rolling off of a car.

Chara distantly took note that Chara’s and Asriel’s arms should have probably ripped off at this point from the sheer speed and force, but were somehow intact.

The world grew colder, the force of slamming into the rubble grew more and more distant. Chara would’ve thought they were falling unconscious if it weren’t the warmth from the snake and Asriel’s body. Chara’s vision of everything else but these two creatures they were holding onto faded into darkness.

And then . . . something shattered.


Shifty wiped the Aaron’s dust off of their prop chainsaw. Finally. With that annoying human out of the way, Shifty can perform a real tragedy. They admit, it’ll be hard to get back into the Ruins, but Shifty was confident that by following Alphys, they’ll find a way.

A cracking sound echoed down the hallway. Shifty spun their head around to see the wall had a new crack. Hmm, the explosive was stronger than Shifty intended. No matter, they’ll-


And then the crack spread. But not just spreading in the wall, but in the air. Shifty’s eyes widened. The cracks in reality started to spiral and spread outwards like glass. No, no, no. Shifty had to load. Shifty had to reset. Shifty had to-



“Are you alive?” 

“. . . No.”

“Me neither.”

Chara pushed their sore body a few inches off the ground. They seemed to be right outside the collapsed artifact room. Shifty and that snake were nowhere to be seen. They looked over to Asriel. He was . . . completely fine. All the wounds and injuries he got during the cave in were completely gone. Chara looked down at their own hands and arms and found they were completely fine. Not even a wrinkle in their gloves.

Chara fully pushed themselves off the ground, a groan slipped from their lips. Once Chara was on their feet they held a hand out to Asriel, but he was already getting up himself.

“So . . .” Asriel began. “Where’s the legendary artifact?” 

Chara closed their eyes. “I’m . . . pretty sure that snake thing left with it after it saved us.”

Asriel hung his head. “Aw man. And I wanted to make history today.” He took a breath. “But if that’s what we had to do to survive I’m fine with-”

“Yeah, yeah, I heard it too bro,” A voice echoed from down the hallway. Chara and Asriel turned around.

“You and Undyne can check on your end, and I’ll check on mine,” the monster said. The monster walking down the hallway was wearing a blue hoodie and a white shirt underneath. His sneakers were untied. He was a short skeleton. Chara and Asriel stood rigid.

The monster stopped, seemingly taking the both of them in for the first time.

“Uh, nevermind Pap, pretty sure I just found the cave in, and maybe the ones who caused it.”

“K-k-king Sans?” Asriel asked. Chara was thankful their brother was there, they didn’t think they could be as articulate.

Chapter Text

There was a solid beat of silence as Chara and Asriel stared at Sans. His face and entire body didn’t so much as twitch as he stared back at them.

“Heh,” he laughed. “King Sans? Now I’ve been told I’m a royal pain but being king takes the crown.” A loud voice on the other end of the line said something. Sans didn’t even flinch the phone away. “What? Not you Pap,” his eyelights looked off to the side, his sockets crinkling, “just talking to some people in Waterfall. Yeah, they’re outside the cave in. No they’re fine, but you and Undyne should come over here to meet them. We’re over by the piano room.” With that said, Sans ended the call and pocketed the phone.

Asriel perked up. “Undyne’s coming here?” he asked.

“Yeah, you know her?” Sans asked.

Asriel scratched the back of his head. “I’m a huge fan of her.”

“Nice, what about you?” Sans asked turning his attention to Chara.

Chara resisted their urge to frown. Something was off about how King Sans was talking. Chara shrugged.

“Who isn’t? I’ll admit, I’m not as worshipping as my Rei, but I like her.”

Asriel blushed. “Chara! I’m not-”

“Did you cause the cave in?” His voice cut through Asriel’s protest. Asriel stiffened, while Chara’s eyes snapped open. They both turned back to Sans. Still standing there. Still watching them. Still smiling.

Asriel waved his hands in front of him. “N-no. Of course not, y-your majesty! We just solved the piano puzzle and then Shifty, well, we’re pretty sure Shifty was the one who caused this . . .” Asriel trailed off. Their gaze moved to the side and their expression became pained and confused.

Chara stepped in. “I know Shifty did it. I saw them use their phone as some type of bomb. They activated it, dropped it by the secret puzzle door, and bolted.”

Sans’ eyelights looked off to the side as he rubbed his chin. “Shifty huh? Okay, I’ll let Undyne know who to look for. But in the meantime,” he looked back at Chara and Asriel. “How about we properly introduce ourselves to each other. I’m Sans, Sans the Skeleton.”

Chara stopped the words, “We know your majesty” from tumbling out of their lips. Asriel looked to them, and Chara shrugged.

“Well, I’m Asriel Dreemurr, and this is my sibling Chara.”

Sans paused. He slowly looked from Asriel to Chara. “Asriel and Chara, huh? Nice to meet some new pals. Put er there.” He reached out his hand.

Chara repressed their mischievous smirk as they smoothly and quickly took the handshake. Chara didn’t have time to revel in the feeling of ketchup exploding between their hands as a noise erupted out.


“Hehe,” Sans laughed. “The ol’ whoopee cushion in the hand trick. It’s always funny.”

Chara’s surprised expression quickly morphed to glee as they saw Sans retract his hand, revealing the miniature, now red, whoopee cushion in his hand.

He looked down at his own glove. “Not that I appreciate a good prank, but you wasting food like that is making me see red.” The corners of his eye sockets crinkled ever so slightly.

Chara shrugged. “You’re right, I’m a demon. You caught me red handed.”

Sans laughed, “Heh,” he looked away from Chara and past them. “Speaking of which. I’m pretty sure we’re going to have to put a cop on the conversation. Because Undyne and my brother just showed up.”

Chara froze. Their head whipped around to see a tall armored figure marching out of the darkness towards her. At first, Chara thought it was her mother. But Toriel never, even on her worst days, marched as aggressively as that. Chara was pretty sure that the boots coming into view were actually making indents in the earth.

Chara’s eyes widened as they finally noticed the face poking out of the royal guard’s armor. Undyne . . . but different? The iconic shiny metal on the side of her face was gone. Instead replaced with flesh, as if lava never touched her face. The only sign of an injury was the eyepatch covering her left eye.

Asriel perked up. “Undyne!” He shouted as he waved at her with a smile.

Undyne’s warpath of justice slowed down as she received the warm greeting, letting the monster farther down the tunnel have more time to catch up to her. Once she stopped in front of the three of them, she scanned them. Her gaze looked over Sans, literally, past Asriel, and landed on Chara. Before Undyne could even think anything about that, Asriel stepped into her gaze and offered his hand.

“Howdy Undyne! My name’s Asriel,” he said cheerfully. “I’ve been a huge fan of yours forever, and I’m sorry that we haven’t been able to meet until now, but I’ve been so busy with my training in Snowdin that I haven’t had a chance. Nice to officially meet you face to face!”

Undyne’s face morphed into confusion. The ridges of her eyebrows scrunched together and her single eye flickered between Asriel and Chara behind him.

“Oh, please don’t fight us. Normally I wouldn’t pass up a chance to spar with you, but,” Asriel trailed off. “Chara doesn’t like sparring and I’m honestly a little shaken up over the whole cave in ordeal.”

“Ah, do not worry Ariel! Undyne is on duty so she only will spar during her offtime with friends and acquaintances,” the tall skeleton monster said. Chara blinked. Either he ran quicker than before, or Chara was getting really distracted by watching Asriel awkwardly interact with Undyne. He was wearing armor, but of an obvious different style and caliber compared to the royal guard, and a red scarf around his neck. “I’m the Great Papyrus, nice to meet you!” He offered his own handshake next to Undyne, and Asriel took it.

That’s odd,” Chara thought. “Undyne doesn’t normally hang out with others, yet he seems familiar to her. Maybe he won in a fight, or at least impressed her? I don’t remember him, but his voice sounds familiar so I might’ve seen him on the show at one point or another.

“And who is . . . Chara?” Undyne asked.

Even from behind Asriel, Chara knew he blinked. He turned slightly and pointed over his shoulder. “They are,” Asriel pointed out.

Chara frowned. They could’ve sworn Dad showed Undyne a photo of them at one point, or at the very least talked about them.

“You mean the human, you know its name?” Undyne asked. Her fist on her side opened up slightly, still tight. Wide enough for a spear to form.

Chara flinched. Okay, that hit too close to home. Chara couldn’t help but remember the disrespect the soul hunters gave them when Toriel stood in their way.

Papyrus looked a bit uncomfortable off to Undyne’s side. His sockets were shifted to look towards her and magical sweat formed on his skull.

“Why wouldn’t they Undyne?” Papyrus asked. “It’s only polite,” he said, stressing the word “polite.”

Before she could respond, Asriel cut through. “Of course I do! They,” he stressed the pronoun, “are my sibling! I can’t believe this! Not only not knowing the children of your mentor, but also attacking them? If you really wanted to kill Chara for their soul, you would’ve done it years ago! Only now, when they’re in front of you, you decide to mercilessly kill them.”

Undyne’s face was extremely confused and angry. Chara couldn’t blame them though, they were feeling about as stunned as she was. Granted, Chara knew objectively, that Asriel loved them. But they’ve never seen Asriel defend them like this. Granted, whenever soul hunters were around, Toriel would be the one scolding and yelling. Watching Asriel from behind, it was like seeing a mirror image of Toriel without the armor.

Before Undyne could interject, Asriel continued. “I can’t believe I looked up to you! Sure, you’re really strong and your fighting is second to none, but I can’t admire someone who is so, so . . . unjust!”

Undyne staggered back, as if physically struck (Although as Chara thought about it, not even a physical blow could knock Undyne like that). Silence filled the hallway. Chara’s eyes nervously darted back and forth between Asriel and Undyne, They were tempted to create a magic knife, just to see if it is possible to cut tension.

“Hey kid,” Sans’ voice piped up. Asriel and Chara looked behind to see Sans standing there still. “What’d you mean about “she would’ve done it years ago?””

Asriel’s eyebrows scrunched together. “Chara’s been Underground for years. Undyne would’ve known about them being here by now, surely. I know Dad talks to her about us.”

Sans paused. “Hey Undyne, why don’t we head out to the lab? From what I’m herring, this has goat to be a misunderstanding.”

Chara perked up at that. “Right! Dad can calm Undyne down. Besides, I haven’t seen him in awhile,” they thought.

Papyrus put a hand on Undyne’s shoulder. “Right! I know we’re all angry or confused, and I’m sure the good doctor can help clear things up!”

Undyne looked at Papyrus, then at Chara and Asriel, then at Sans. She threw her hands up, and turned around. “Fine! Let’s go to the lab. There’s something weird with these two, and I want to know what’s up!”

Sans raised a finger.

Undyne whirled on him. “Don’t start.”

He put the finger back into his pocket.

Undyne marched ahead, and Papyrus followed.

Asriel took a calming breath, and followed as well. Walking next to him, Chara threw an arm around him.

“Hey Asriel, thanks. Again,” Chara said.

Asriel smiled. “Anytime Chara.”

Sans watched the four of them retreat down the tunnel, before he turned around and walked in the opposite direction. He vanished, like an eraser wiping clean a whiteboard.