Remember: Spoilers for Undertale, my story, and R.I.P Lynn's are contained within this story.

If you'd rather not be spoiled in any of those three ways, please stop now and go read the other stories or play the game. (It's worth it!)

If you need another reminder/overview of either of our stories, please go back to chapter one or two to check them out.

Thanks again to R.I.P. Lynn for making this possible.

Now, time to check on everyone!


Warning: If you have not read 'UNDERTALE: (file name not found)', PureTale/Purity, or played Undertale, there WILL be spoilers for each of them. Undertale is owned by Toby Fox. 'UNDERTALE: (file name not found) is owned/created by R.I.P. Lynn. I, myself, only own/have created the O/Cs and personalities of the PureTale timeline. Enjoy!

I have been given express permission to use her work and to write this Cross-Over. Thank you R.I.P. Lynn!

Quick Note: Never read Puretale/Purity, but simply want to read this? Or maybe, you need a quick refresher course? Either way, here's a quick summary of PureTale/Purity before we start the story. Shout-out to R.I.P. Lynn, who was the masterful author/writer who created 'UNDERTALE: (file name not found)'. Please, if you have not, go read her work of art! I hope I do it Justice...

Previously on PureTale/Purity:

In the PureTale Timeline… Frisk completed a Neutral Run(No RESETs) without killing anyone, except for Asgore's death from Flowey. Before a RESET could happen, Gaster kidnapped Frisk and took the six Souls in a bid to take control of the Timeline. You see, he could see beyond his timeline, and grew fearful of other 'beings' and 'entities' who might come to this timeline and destroy it.

Six months later, Alex fell into the Underground, looking for his best and only friend: Frisk. He had a silver Soul of 'Purity', which had the unique ability to 'Purify' Souls, which returned them to their purest states and traits, removing things that don't belong. It also had the ability to take on other traits when exposed to enough of them. During the journey, he met and befriended all of the Monsters, starting with Sans' rescue from a very angry Flowey, before soon coming up with a plan to rescue Frisk from Gaster and the Void.

After traveling and gathering the needed supplies from around the Underground, Sans and Alex worked together to repair his machine despite all of Gaster's numerous attempts to stop them. Soon, they finished and rescued Frisk from the Void, but, doing so, they ended up bringing Gaster back too. After defeating him by turning the six Souls against him they forgave Gaster, before Frisk undid the previous six months with a LOAD in order to get a True Pacifist Ending and undo Asgore's death. Alex, because of the power of his Soul, remembered the previous timeline and left for Ebott immediately.

Back Underground, they brought Gaster back again using Sans' machine, before then restoring everyone's memories and traveling to Asgore's Castle. Flowey soon came forward, taking the Souls, and turning into the 'god of hyperdeath'. After defeating Asriel and breaking the barrier, the Journey concluded with Gaster gathering enough essence from the Void to either bring Asriel's Soul back or restore Chara's body and Soul. Both begged for Alex to chose the other, but he ultimately decided to save Asriel since Chara still had some part of her Soul within Frisk. All together, the monsters went out onto the surface and the Dreemurrs reunited and adopted Frisk and Alex.

Fast forward several months and Monster integration is going pretty well as school began to start up. Gaster soon created the QMA(Quantum Multiversal Accelerator) Prototype and gained access to a small portion of the Multiverse. With access to alternate timelines, he soon found his first alternate timeline. Here, a genocide was occurring, and that timeline's Gaster made a deal with him: If Alex came and stopped it, then he'd donate enough essence to bring back Chara for them. Eventually, Alex succeeded and the Dreemurr family was finally fully reunited. Another product from this encounter also provided a new ally in the form of Rindie, a power entity with a drive to do good. But, at the same time, Core Frisk wasn't very pleased with Gaster.

The timeline jumps soon caused new issues, though. An error with the QMA fractured the vortex as it expanded, sending some of them to Underswap and some of them to Underfell. It was here that Alex soon learned the dangers of his powerful Soul. While battling to save his friends in Underfell, he gave into a small amount of Hate and his Soul turned black. You see, another ability of Alex's Soul is that if he feels a strong enough emotion, or is injected with a concentrated dose of a particular trait, his Soul will temporarily take on that trait... except in a more powerful, more 'pure' state. As such, he was consumed with 'Pure Hatred' until he eventually snapped out of it. From this point on, he became terrified of giving into these traits and hurting those he loved.

After many other misadventures with the QMA, including accidentally letting Betty(FEAR) into their timeline, the fight for their timeline quickly grew more intense. After stopping Error Sans from destroying them and gaining a new ally named Alric, they soon fought this 'Entity', who's ultimate goal was to take control of the Timeline and shape it in the way he thought it was always meant to be. Up his sleeve was another unique trait: Creativity. With it, the one with the most could shape the timeline as they saw fit. In other words, "become god of the timeline", making it his own. Eventually, after teaming up with Jordan Sower, the other person with Creativity(aka swrWriter), they managed to stop the Entity, strip him of his creativity, and then destroy him.

By the end of it, everything was calm again and things were looking up. Thanks to the QMA, Gaster continued his research and soon gained help from Core Frisk and a few others, who showed him the true size of the multiverse. With this knowledge he soon discovered a way to upgrade the QMA to be able to connect to the rest of it and perfect his technology…

Together with Sans and Alphys, the three of them soon got to work, despite the numerous warnings from Core, and it was nearly complete...

And now, today, the newly upgraded QMA is being booted up… I wonder which timeline they'll find?!


Chapter One: What could possibly go wrong?

The work-spaces and tabletops around Gaster's lab were covered in various books, devices, and chemicals. The scientists, here, have been working tirelessly for weeks on their masterpiece, the second greatest invention by Monsterkind (The first being the Core). They call it the QMA, which stands for the Quantum Multiversal Accelerator. With this device, Gaster has successfully connected to and discovered countless timelines and alternate universes.

Doctor Gaster stood before his two assistants as he prepared to boot back up the QMA, wearing his normal outfit. He wore a black turtleneck and a black pair of dress pants and shoes, while wearing his standard white lab coat over his normal clothes. Sans and Alphys sat at their respective seats and looked directly at the doctor. Sans wore a usual lazy outfit under his lab coat, consisting of his signature blue coat, a pair of black basketball shorts, and a pair of shoes. Alphys wore a skirt and top underneath her own lab coat, but the coat covered her clothes completely.

Gaster smiled as he looked at his two assistants, "ALRIGHT, IT IS TIME…" He nodded at Alphys, "DOCTOR ALPHYS, IF YOU'D BE SO KIND."

"O-of course." She stuttered, quickly turning to her keyboard and typing various commands into her console. They could hear the nearby device turning on. It was a large, octagonal frame, with the individual joints displaying a Soul-like heart on it. It looked very similar to the 'portal frames' you'd see in movies. There was a large cable connected to the bottom of the QMA, which led directly to the Core, which provided the power required to punch through the barrier between timelines and universes.

"what do ya need from me, dad?" Sans asked, staring at Gaster, ready to do whatever was necessary.

Gaster nodded, "MONITOR THE READINGS, SANS. I WANT TO KNOW THE MOMENT ANYTHING GOES WRONG."

"you got it g." Sans replied, turning back to his monitor to keep track of the data. Various charts and numbers began appearing and shifting on the screen as the machine began to come to life.

"SANS, TIMELINE STABILITY?"

"it's at a hundred percent still."

"PERFECT." He replied, "DOCTOR ALPHYS, STATUS?"

Alphys turned toward Gaster, "Core energy flow i-is normal. Startup in th-three, two, o-one."

On cue, the QMA began to buzz and vibrate, making all three of their heads turn toward the device. All eight heart symbols on the joints lit up and began to emit a white light, just as a black vortex opens within the frame. After a few moments, the device stabilized and stopped shaking, telling the three of them that it was successfully reactivated.

The three monsters couldn't help themselves and let out a cheer at their success. Gaster smiled proudly. This reminded him of the first time he activated the QMA. Only this time… this time it was greatly upgraded. Thanks to various bits of information from Core Frisk, Jordan Sower, and a few other individuals, he'd discovered a way to increase the QMA's range, allowing access to the entire multiverse. Or, at least, in theory.

Now he'd be able to discover and connect to timelines that he'd never even thought were possible. Imagine it… Countless unknown Soul Traits. Countless timelines with alternate histories, doppelgangers, and stories. Any and every alternative to things he's discovered were now waiting for him. Quite frankly, Gaster felt like a kid in a candy store. A kid who could pick out any and everything he could ever want. To say he was excited would be an understatement.

Alphys turned to Gaster with a wide smile, "S-so what's next Doctor?" She said, excited about the possibilities and discoveries too.

Sans comically raised his hand, as if he were a student waiting to be called upon by the teacher. Gaster looked at Sans and motioned for him to speak, "i vote for a break."

Doctor Gaster chuckled and shook his head, having expected something like that to come out of his son's mouth. Finally, after a moment, he shrugged, "ALRIGHT, BREAK TIME… IN A MOMENT. SANS, FINISH SETTING UP THE ALGORITHM. I WANT THE QMA TO SEARCH FOR SOUL ANOMALIES, FOCUSING ON THE MOST UNUSUAL OR POWERFUL." He paused for a moment before smiling, "THEN, WE CAN TAKE A BREAK."

Sans turned back around toward his monitor and quickly typed a few commands into the device, "done, and done. break time." And with that, Sans vanished, likely disappearing to the break-room's couch to enjoy another nap. But… he did earn it. They all did after all of that hard work. Now they all had to wait until the QMA finds a timeline of interest, and Gaster could hardly wait.


Gaster took a sip out of his Father's Day mug, allowing the delectable taste of coffee flow into him. The black mug read '#1 Dadster', a gift from Sans and Papyrus. He smiled as he continued to drink his coffee in the relaxing environment of the break-room. Sans, like usual, was napping on the comfortable, black couch in the corner, while Alphys sat at a nearby table and enjoyed a sickly, yellow soda of her own.

It's been about half an hour since the QMA was reactivated and there haven't been too may results so far. Sure, there were a few timelines that had unique energy signatures, including one that looking similar to this 'Underswap' timeline, but more like the signals were swapped around in pairs. Unfortunately, other than that, not many new, exciting timelines have been discovered. That timeline could wait. Gaster wanted to start at the top, then work his way down from there.

Gaster looked up and pulled out his pocket watch. 12:05 pm. Papyrus would be by with the kids soon enough since they had an early day at school, and both Toriel and Asgore were busy this afternoon with meetings, so the skeletons had been tasked with watching them, not that it was that big of a deal. He really hoped some sort of profound discovery would be made before they arrived so he might show them his progress, but he wasn't too sure that would happen.

As Gaster downed the last of his coffee, a beeping sound echoed throughout the lab. It wasn't an alarm, thank God, it was Sans' algorithm signaling a successful find. Gaster grinned as he put his empty mug down on the counter softly and turned toward Sans and Alphys.

Alphys hopped down from her seat and Sans was already standing beside Alphys, spooking her from his sudden appearance. She jumped a bit, causing Sans to chuckle.

"Could y-you maybe not?" She said, narrowing her eyes at the pranking skeleton.

Sans shrugged, "c'mon doc, you should be used to it by now."

She frowned and shook her head, "I'll never get used to you breaking the laws of physics."

Sans grinned, "guess you can't physically wrap you head around this then."

Gaster, despite his excitement, chuckled, "ALRIGHT YOU TWO, YOU HEARD THE MACHINE. LET'S GO."

They all proceeded back to their work stations and began pulling up the data being gathered from this timeline in particular. Gaster was beaming. There must have been some amazing, profound reason why this timeline was singled out! Then, Gaster started looking at the data.

Base readings of the timeline suggested that it was similar to many other timelines, including a few others that Gaster had found earlier. That means that there were no massive swaps or changes to that universe at conception. But, after looking at it a bit more, he saw some very odd data points. There was a unique, never before seen Soul Trait in this multiverse. In fact, this Soul Trait might be exclusive to this single timeline and maybe a few other branching ones.

"DOCTOR ALPHYS, FOCUS THE SCANNER ON DATA POINT 2390131." Gaster called out. "SANS, FOCUS ON DATA POINT 11796565."

Alphys nodded and did her best to amplify the signal and clear up any issues for that particular data point, as Sans did the same on his screen. Soon enough, more data was shown on the monitors about those specific data points.

"hey doc, what're we looking at here?" Sans asked, having just finished focusing his scanner.

Gaster smiled as he examined the data, speaking without looking away, "THIS, SANS, IS THE SIGNAL FROM THE TIMELINE." He was pointing toward Alphys' data, before then pointing at Sans', "AND THIS IS THE SIGNAL FROM THE SOUL TRAIT."

He leaned forward and focused on Alphys' data first, "DO YOU SEE THIS MASSIVE JUMP?" He said, motioning toward the generated graph, which shows a massive change and a few smaller ones, "THESE ARE ALTERATIONS TO THE TIMELINE, ITSELF. THIS MEANS IT HAS UNDERGONE MASSIVE CHANGES, MAKING IT FAR DIFFERENT THAN IT ORIGINALLY WAS."

Gaster minimized the graph and pulled up San's data on the Soul Trait, "AND LIKEWISE, THE SOUL IN QUESTION HAS RELEASED LARGE AMOUNTS OF POWER OVER THE COURSE OF THE TIMELINE'S HISTORY, MAKING IT ONE OF THE MOST POWERFUL SOULS I'VE EVER SEEN."

Then, Gaster pulled both graphs up and overlaid them with one-another. The points in which the Soul released the most energy and the points in which the Timeline changed were all overlapped, "AND TOGETHER, THE SOUL'S POWER AND THE TIMELINE'S COURSE WERE CHANGED TOGETHER, MEANING ONE OF TWO THINGS. EITHER THE SOUL IS BOUND TO THE TIMELINE DIRECTLY, OR THIS SOUL IS POWERFUL ENOUGH TO ALTER THE TIMELINE."

Sans looked at Gaster questionably, "like determination? or creativity? we've seen the effects of them before on the timeline, but…"

Gaster nodded, "YES. IT SEEMS THAT IF IT IS ALTERING THE TIMELINE, WHICH IS MORE LIKELY THAN THE FIRST OPTION, THAN IT IS BOTH MORE POWERFUL THAN AND FAR DIFFERENT FROM DETERMINATION. POSSIBLY EVEN EXCEEDING CREATIVITY."

"B-but h-how?!" Alphys asked, shocked by this information, "D-determination is the only thing that can radically change the t-timeline, and all i-it does is rewind t-time?"

Sans narrowed his sockets as he looked at the data, himself, "hmm, it seems that the timeline didn't just rewind… it was completely altered. it's almost as if the change was so massive that every single event was changed simultaneously."

"Th-that'd take a l-lot of power to do that."

Gaster nodded, "YES…" He paused and turned around, looking at his two partners, "THIS IS EXACTLY WHAT WE'VE BEEN LOOKING FOR. A SOUL MORE POWERFUL THAN DETERMINATION. STRONGER THAN CREATIVITY. MORE ADAPTIVE THAN PURITY. MORE TERRIFYING THAN FEAR." Gaster smiled widely, excited by this discovery. "SANS… PREPARE TIMELINE CONNECTION."

Sans flinched a bit at this, "g-gaster… not that i'm not excited about this too, but i don't think that's a good idea." Gaster turned and faced Sans, listening carefully, "i mean, we haven't even tested the timeline connections with the qma since we upgraded it. we should probably give it more time."

Gaster frowned and shook his head, "AS MUCH AS I UNDERSTAND SANS, THAT'S SIMPLY NOT AN OPTION. WHAT IF ANOTHER SPIKE FROM THAT SOUL PREVENTS ANY FURTHER CONNECTION? WHAT IF THAT SOUL CHANGES THE TIMELINE AGAIN? WE MUST CONNECT AS SOON AS POSSIBLE…" Gaster paused and sighed, "BUT WE WILL NOT GO IN JUST YET. WE WILL AT LEAST WAIT TO MAKE SURE THE CONNECTION IS STABLE AND SAFE."

Sans nodded, "alright, guess that's better than nothin'." Sans typed in a few commands and the QMA began to connect to this new timeline. The white hearts in the joints soon all changed to different colors and the vortex, itself, began a kaleidoscope of colors, signaling the connection.

"PERFECT. RUN DIAGNOSTICS. I WANT TO KNOW HOW STABLE THE CONNECTION IS, HOW THICK THE SPACE-TIME FABRIC IS HERE, AND ANY OTHER RELEVANT DATA." Gaster commanded, prompting Sans and Alphys to set up a few other things.

Finally, a moment later, the door to the lab opened and four others came into the lab. "-AND THAT IS HOW WE LEARNED THAT COOKING WITH FLAMETHROWERS WAS NOT A VERY VALID METHOD TO COOKING PASTA." Papyrus explained as he walked in with three humans. Papyrus wore his orange and white battle-body, like normal, as he led them into the main lab. "OH, HELLO DAD. HELLO SANS. HELLO DOCTOR ALPHYS."

Gaster turned and smiled warmly, "AHH, HELLO PAPYRUS, HOW'S YOU'RE DAY BEEN?"

Papyrus beamed, "IT'S BEEN EXCELLENT. UNDYNE AND I TRIED COOKING SPAGHETTI WITH FLAMETHROWERS THIS MORNING, AND THEN I WENT TO PICK UP THE CHILDREN FROM SCHOOL."

Alphys' face paled as she turned to look at Papyrus, "P-p-papyrus… wh-where'd you do th-that?"

Papyrus continued to smile, "NOT TO WORRY DOCTOR, WE MADE SURE TO DO IT IN THE SAFETY OF YOUR BACK YARD. NOTHING WAS DAMAGED EXCEPT FOR YOUR BACK FENCE AND YOUR GRASS. BUT IT CERTAINLY WASN'T FROM THE STREAM OF FLAMES WE USED FOR OUR COOKING SESSION!"

Alphys sighed but was at least partially relieved. Luckily, it sounds like the house, itself, was still in one piece. "O-ok…" She said as she resumed her work.

"Hey Doctor Gaster!" Frisk said enthusiastically, wearing her favorite blue and purple sweater, while Alex simply smiled and waved, too caught up in the music he was listening to on his phone. Chara swiped once and disconnected Alex's earbuds from his phone, making him frown.

"What the heck was that for, Chara?" Alex asked, putting his earbuds and phone away. He wore a pair of blue jeans and a red t-shirt.

Chara shrugged, "Because you should stop listening to that trash, you're with your girlfriend, after all. Doesn't she deserve your undivided attention?" She teased. She wore her classic green and yellow striped sweater with a green shirt underneath and a pair of brown pants. Alex blushed a bit, but felt Frisk squeeze his hand a bit to comfort him, making him smile.

"sup kiddos, where's the goat?" Sans said with a smile.

Chara snickered a bit, "Azzy didn't do very good on his last English test, so Mom is making him go to tutoring this afternoon."

Frisk frowned and scowled at Chara, "That's because SOMEONE decided to give him the wrong stuff to read and study."

Chara put up her arms in defense, "Hey, it's not my fault he fell for it so badly. He should have realized that 'stupid' was too simple of a vocabulary word."

Sans chuckled a bit, "hehe, yeah but i'm pretty sure tori's gonna find out real quick what happened."

Chara shrugged, "I'll cross that bridge when I get there."

"Hey Gaster, what's going on in here? You doing more work with the QMA?" Alex asked, taking a few steps forward, taking Frisk with him.

Gaster smiled and nodded, "YES, THANKS TO RECENT ADVANCES, WE'VE FOUND MORE TIMELINES THAN WE ORIGINALLY ANTICIPATED."

"yeah, we just found one that probably has the most powerful soul ever." Sans supplied, smiling at them from the work bench as he said that as nonchalantly as possible.

"Woah! Really? That's so cool." Alex said, staring at the swriling vortex within the QMA.

Chara crossed her arms, "I hate to be the one that sounds like Core Frisk, but is this really a good idea?" She asked, staring at the swirling vortex within the QMA.

Frisk turned away from the vortex and looked over at Chara, "What do you mean?"

Chara rolled her eyes. "What do I mean? Newsflash Frisk and Gaster, that device hasn't exactly been beneficial to us. Let's see… it sent Alex into a genocide, all of us into Underswap and Underfell, it gave us Betty and the Soul of Fear, and it let Error Sans in here. If anything, we should just turn it off and destroy it."

Gaster frowned for a moment before chuckling for a second, "NEWSFLASH CHARA, YOUR GIRLFRIEND WOULDN'T EXIST IF IT WEREN'T FOR THIS. IN FACT, YOU'D STILL BE A GHOST IN FRISK'S HEAD IF THIS MACHINE NEVER EXISTED. LOST OF GOOD HAS COME FROM THIS. YES, SURE, THERE'S BEEN SOME ROAD BUMPS ALONG THE WAY, BUT SO MUCH GOOD HAS COME FROM IT TOO." Gaster countered.

Chara blushed and looked away, "Y-yeah… I guess you're right about that…"

Frisk snickered at Chara's blush, quickly earning a hard stomp to her foot. "Ouch!" Frisk complained, making Chara snicker back.

"Well, that's what you get Frisk!" She said, crossing her arms and looking away.

Alex comforted Frisk by pulling her into a light hug and smiled at Chara, "Yeah Chara. What could possibly go wrong?!"

She narrowed her eyes and turned back toward Alex, "I hate you Alex." Alex couldn't help but snicker at that as she continued, "Of course, you had to go and say that, didn't you?!"

Alex chuckled and smiled, "Thanks Chara, and yeah, I kinda did need to say that."

Sans turned around toward Gaster, "hey g, we got a problem."

Gaster quickly turned around and walking over to Sans and his monitor, "WHAT IS IT?"

Sans pointed to the stability readings on his screen, "the connection between this new timeline and ours is strained. the barrier around their universe is fluctuating too rapidly, warping the connection. stability is plummeting."

Gaster sadly nodded, "ALRIGHT, COMMENCE SHUTDOWN PROTOCOL."

Sans nodded and began to power down the QMA, cutting off the power supply from the Core. But… for some reason, the QMA remained active despite the lack of power maintaining it. "u-uh… dad…" Sans muttered as the QMA began to shake, starting off slowly but quickly increasing in intensity.

Gaster turned to Alphys, tone becoming urgent, "ALPHYS, TRY TO OVERRIDE THE QMA. SANS. PAPYRUS. HELP ME HOLD THE QMA TOGETHER!"

Alphys began typing ferociously as the three skeletons used their blue magic to hold the QMA together and as still as possible. Alex, too, jumped into action as he pressed a blue button on his bracelet. As soon as he did, the blue liquid within it drained into Alex, turning his Soul a vibrant blue color. He was filled with Pure Integrity.

Using his new blue magic, Alex joined in to help the skeletons hold it together. Frisk and Chara too, despite their lack of blue magic, joined in my forming magical constructs to try to physically restrain the device.

Unfortunately, despite the six-people trying to hold the QMA together, the joints could no longer take the strain and they disconnected from one another as the QMA collapsed. Even worse, the vortex remained behind despite the QMA breaking apart.

"DAMMIT. ALPHYS, PUT UP THE MAGICAL INHIBITORS! WE NEED THIS VORTEX CLOSED!" Gaster commanded as said vortex began to osculate and fluctuate, increasing in size.

"D-doctor, they're almost online." Alphys muttered, before the magical inhibitors turned on successfully. "They're o-online."

Suddenly, the vortex exploded, increasing in size greatly and swallowing the three humans and the three skeletons, before collapsing in on itself. The remaining monster in the lab flew backwards, off of her chair and against the wall. She soon fell to the tiled floor unconscious.


The dinosaur-like monster laid like that for over an hour, before she was found like that by Undyne. She wore a pair of black combat boots, a pair of dark blue jeans, and a black tank top, all covered in soot from her and Papyrus' misadventures in cooking earlier that day. Alphys' girlfriend came over and tried waking her up, running to her side immediately upon noticing the destruction within the lab.

"A-Alphys?! Say something, please!" She said, gently holding her sleeping form, only relaxing slightly when she felt her breathing. "What… what happened here?" Undyne wondered aloud as she looked around, seeing that the QMA was shattered into millions of pieces. She looked around her, trying to see if there were any other survivors. Luckily, no specks of dust nor drops of blood were found. Unfortunately, there was only one conclusion to be drawn by this scene…

Gaster… Sans… Papyrus… the kids… they had all must have been sent to another Timeline…

And as much as Undyne wanted to say they'd be ok, she didn't know much about all of this timeline nonsense other than her experience with a more-red doppelgänger who was out for blood. And based on the scene around the lab… this wouldn't be an easy fix…

She just hoped that wherever they ended up, that they'd be ok…