Gonna lighten things up here for a bit because that last chapter was emotionally exhausting. Also, now we get into the meat of this fic!

P.S. The designs of the characters in Underfell are not mine and can be found in the 'underfell' blog on Tumblr if you're curious. They are all precious, evil babies that deserve some tough love. Especially Chillby.

CHAPTER 6- UNDERFELL PT.1

There was a strange song playing in the background as Sans began to regain consciousness. It sounded like a choir of people humming discordantly but somehow managed to be mellow and relaxing, if a little quirky.

The little lights in Sans' eyesockets blinked a few times before focusing.

Frisk lay on the navy-colored dirt beside him, just beginning to stir as well. Mustering his strength, Sans sat up in a body that felt ungainly to him. Why did he feel so unusual? He couldn't remember, but the term: 'out of body experience' wound its way to the forefront of his mind. Had he died again? The thought flitted away before he could fully process it.

Looking around, Sans was surprised to discover that he and the human had collapsed smack-dab in the middle of Temmie village. But which Temmie village? When? Which when? God, he hated time travel.

"HoI hOi!" One of the Temmies scurried over and pushed her round head right into Sans' personal space. "Not sEe u com In!" It yapped. "Want buy TeM fLakes?"

Sans didn't have time for this right now. Gently, he put his palm to the top of the small Tem's head and picked her up like a basketball. Slightly less gently, he dunked her into a wide crack in the cave wall.

Frisk giggled at his antics, having apparently woken up behind him.

She blinked blearily and rubbed her forearm across her eyes. She looked about as haggard as Sans felt right about now, and her brow was creased in thought. As if she were trying to remember something too. Now that was unusual. Frisk never forgot timelines.

"When are we?" She asked, still rubbing her left eye like it was bothering her. Sans took a deep breath, feeling deeply unsettled. Something had happened. Something really, really bad. He could feel it in his bones and it made him angry that he couldn't remember.

Sans helped Frisk to stand and wondered at the fact that he didn't feel uncomfortable in her presence despite still him still retaining the memories of those past time lines where they'd... had differences in opinion. Mostly regarding murder.

He had been about to reply when Frisk dropped her hand and stared at him full in the face. With one regular, dark eye... and the other a burning electric blue.

It felt like a dam breaking in his mind.

The argument with Papyrus, the memories of trying and failing to protect the previous children. Confronting frisk, learning of her deal with Gaster, getting drunk. Hugging Papyrus, entering the burning house, Gaster. Fear, burning, watching his brother holding his dust-covered hoodie to his chest. refusing.

It felt like falling through ice into frozen water. That had happened. To him. To Papyrus. His Papyrus. Sans heard someone cry out as he clutched his skull between his hands, falling back to his knees. It was only as he felt Frisk's arms around him, comforting him and getting the fur lining of his hoodie soggy with tears that he realized the sound had come from him.

New body, new hoodie, he supposed.

He felt claustrophobic, but not from Frisk's presence. He felt stifled by reality itself, and by the presence he knew was surely watching.

"He CaN't C u heRe." Came a mewling voice. San's vision was swimming with radioactive-blue tears as he opened his eyesockets to find a Temmie wearing a college graduation-cap staring up at him. There was more intelligence behind those beady eyes than he'd ever seen from a Temmie.

"Who? Gaster?" Frisk asked, turning to face her so as not to be rude. Sans resented the loss of her comforting embrace momentarily.

The shrewd-looking BussinessTem's fur stood on end at the mention of the name but she nodded briskly.

"TeM VilLagE proTeCted." She continued. At Sans and Frisk's puzzled stares the Temmie simply gestured up cryptically. Sans had always known Temmie village was a universal constant. Always unchanging and like an ant-hill of shortcuts, most of them nonsensical and some of them leading nowhere at all. He'd always avoided the place for that reason.

But now a thought struck him: Maybe those empty paths had gone somewhere? Maybe they just hadn't led anywhere he could go. Now, looking around the room, Sans could see the trails leading off through time and space. Some were obvious, but others so craftily hidden or so small he'd never noticed them before. Those, he could see now, led to completely different universes.

Frisk stiffened beside him suddenly, pulling Sans out of his revelation.

"I... can see them." Frisk whispered, her eyes as wide as they would go.

Sans didn't have to ask what it was she could see as he watched her left eye glow with his magic. She could see the shortcuts too. How many of them she could find and whether or not she could access them had yet to be determined.

"buT... CaN't steY 4EvEr." The Temmie didn't seem to be following their whispered exchange and was going right ahead with her monologue. "U tWo GotTa keeP mOvIN."

"Where?" Frisk asked, taking the reins of the situation. Sans still didn't trust himself to speak. He didn't want to even think in case he thought about... Sans derailed that train of thought hastily.

Temmie looked at one of the closest shortcuts. It didn't lead anywhere in this universe.

"Okay." Frisk said determinedly, delicately helping Sans to his feet again. He wondered at how she could manage to be so calm about all this. About leaving their fucking universe to escape the void-crazed, god-like monstrosity that had been Sans' former boss and-

Again his mind recoiled from that line of thought.

Weird. But there was no point dwelling on it.

Stepping into the shortcut was easy as ever, just like taking a step. There was a slight squeezing sensation as they moved between the folds of time, a moment of weightlessness

and then a strong gust of wind as they emerged into the Snowdin forests right outside the Ruins Door.

It was night out, Sans thought for a moment. Scattered memories of living on the Surface tried to help him understand the unusual darkness of the forest, but that was nonsensical. There was no night underground.

Frisk coughed beside him and Sans turned to find her shivering violently. It must be very, very cold. Quickly, he removed his thick hoodie and helped her into it.

"T-thanks" She chattered, zipping it up and burying her nose in the fluffy hood.

"no problem, bucko." Sans felt his grin reach his eyesockets despite the bizarre situation. She looked cute in his hoodie.

"I wonder what's different about this universe." She pondered, her voice muffled by the thick fabric.

"guess we'll see, huh?" He replied, taking her under his arm protectively.

...

After a long, cold(for Frisk at least) slog through the snow Sans was relieved to finally see the cozy glow of Snowdin up ahead. He had been perturbed by the lack of puzzles on their way through the mountains(not even a single trap spaghetti!), but Sans supposed that anything was fair game now in terms of timeline fuckery. God, he needed a drink.

"keep yer hood up, kid." Sans whispered to Frisk as they entered the town proper. The monsters were looking at them suspiciously and without even a hint of their usual kindness. Everyone was dressed in menacing blacks and reds and golds.

It seemed they'd come to the wrong neighborhood.

Frisk nodded, sensing the other monsters' hostility and drew her hood down over her face until only the barest glimmer of her blue eye was visible in the shadows.

Deciding it was better than breaking into his alternate self's home for shelter, Sans steered them both towards Grillby- er- Chillby's bar. So that was how this universe was going to be. Great.

The air in the dive was devoid of grease, making Sans immediately decide he wanted nothing more to do with this backwards universe. He took the bar stool that would have been his usual one and was interested to discover that the cushion had the same, squished feeling that his own had. Huh. Frisk took the stool beside him, rubbing her arms through the hoodie to get some warmth back into them.

"So what's the plan?" Frisk asked, ready to take on the next challenge even if she was practically dead on her feet from exhaustion.

"that's a good question." Sans said quietly, absently peeling back a corner of the pristine varnish on the bar-top with his thumb-bone. "first. we need to undo the mess you made by getting the other souls back where they belong."

Frisk wilted a little, accepting the blame entirely.

"then we need to get back to our own universe and timeline, which'll be the tricky bit."

"How will we even find them again? I can see all these paths now... but it all seems like such a mess." Frisk gestured at the gaping holes in space-time throughout the bar that only they could see.

"messes are my speciality," Sans winked. "we'll find a way. after all, my little bro needs me, y'know? he gets real cranky without his bedtime story." He felt his grin slipping again but couldn't bring himself to fix it. Besides, there was no point hiding his emotions around Frisk anymore.

But now it seemed they had another problem.

Sans could feel the dour glares of the other patrons in the bar on their backs as they sat there. One of the Guard Dogs, a Greater-sized Rottweiler even let out a low rumble. Feeling the tension, Sans noticed that Frisk's hands had begun trembling as she gripped his hoodie.

if that's how they want to play, then fine.

Giving Frisk's trembling fingers a reassuring squeeze, Sans turned around in his stool to face the rest of the bar. Yep. Everyone was definitely riled up about them being there.

"what." He asked the room at large, cracking his knuckles for effect. "you guys got a problem?" Sans let his grin shift into something ugly as he stoked the flames of his newly-augmented magic, letting it course through his body like an electric charge.

Then, on his chest, he was shocked to see his soul manifest.

Now he understood how they'd escaped Gaster. Why Sans felt so much more powerful and why Frisk's eye had turned blue. The soul that hovered right above his solar plexus consisted of two different halves: The left side white and the right side a deep, crimson red. He had part of a human soul inside him. Frisk's startled gasp beside him made her thoughts on the situation clear.

The atmosphere in the bar changed instantly.

Lesser-Rottweiler ducked under his table with a little whine, Dogamy and Dogaressa huddled together for protection and even Doggo went perfectly still.

Sans smirked at their quick submission, even if something about it unsettled him.

"bunch'a creeps" Sans muttered as he let his now-burning eye sweep over the room one last time before settling back onto his stool. The room was silent as Chillby brought out two servings of salad and a plastic squeeze-bottle of mustard that he set between them with a cold stare. Sans looked down at the vegetables in disgust.

"What's wrong with them all?" Frisk asked quietly, still obviously shaking from discovering that they'd effectively traded parts of their souls. However, it had probably been ages since she'd eaten so she dove right into the salad. "Why're they -munch munch- so scared of -munch- you?"

Sans pushed the salad away and went for the mustard. Not his favorite beverage but it'd have to do. "i get the feelin' that people aren't so nice in this universe. if that's the case, i wouldn't put it past alternate me to be the worst a' the bunch." San's forehead crinkled at the admission. "eat quick, kid. we need 'ta find somewhere safe to sleep."

"Safe from -munch- who? Ga-" Frisk stopped herself before uttering the name. She didn't want to attract his attention to them, superstitious as that was. "-Him?"

The grin on Sans' face faltered.

"nah. safe from me."

.

.


The Alpha Universe Papyrus knelt where he'd been kneeling for hours now, with no intention of moving. The ground around him had taken on an orange-tinted glow from all the orange-tinted tears that had been falling on it. Papyrus shuddered as another wave of grief broke over him and his fingers tightened further on the dust-covered hoodie he was clutching to his chest.

"Shouldn't we do something for the poor dear?" Mettaton asked from where he was standing with the others some distance away. Papyrus could hear them talking about him clearly, but he just couldn't bring himself to move. He never wanted to move again. He'd just turn to stone because then at least he would have to feel... this.

He didn't look up as the tall, white shape of Toriel approached and then knelt beside him. She placed a loving paw on his back and made reassuring, motherly noises. It felt kind of nice.

"Do you need anything?" She asked softly, her voice full of concern.

Papyrus shook his head and stared straight ahead, not wanting to break into tears again. Not in front of everyone.

"Okay. That's okay. Dr. Alphys is looking into the anomaly that caused the fire in the first place. We are going to figure out what happened." Toriel's heavy paw felt comforting on Papyrus' spine and he felt guilty that it was him being comforted right now. That there was nothing anyone could do to comfort his brother. Or the human.

"I-I f-f-found something!" Alphys voice broke the leaden quiet of the cavern as she rushed out of the house like it was still on fire. "H-ere! L-look!"

The little yellow-scaled monster practically slid to a stop in front of Papyrus, causing him to forget his pain long enough to be curious. She was cradling a little glass vial very carefully between her claws, holding it so that the faint, red light it emitted could be seen by everyone.

"Is that a... piece of the child's soul?" Toriel asked, her voice full of awe and disbelief as she looked at the tiny splinter of red.

"M-more than that!" Alphys seemed buzzing with frantic energy. "I r-ran some... t-tests. There are... t-traces of Sans' s-soul in there too!"

Papyrus couldn't disguise the sudden hope that welled up from his empty chest and onto his face. He couldn't smile, not right now. But he wanted to. He held Sans' hoodie closer to him, willing his brother to come back.

"But how is that possible, Alphys Darling?" Mettaton and Blookie were both crowding around now as well.

"I-I'm... not... sure. S-since they're both... g-gone... it doesn't make sense t-that any p-piece of their s-souls would remain intact. I... d-don't want t-to get anyone's hopes up..."

"BUT IT'S SOMETHING, RIGHT?" Papyrus asked, speaking for the first time since his brother had dusted. His voice sounded creaky.

Alphys looked like she really didn't want to give him any illusions about his brother coming back. Something inside Papyrus told him that she'd made that mistake before, but he couldn't place the source of the memory.

"I-it's r-r-eally unlikely... s-so... p-please don't be m-mad if it t-turns out... t-to be nothing, okay?" Alphys muttered.

Papyrus nodded, accepting.

"TELL ME HOW I CAN HELP." Papyrus said, standing back up to his full height. He contemplated the hoodie in his arms for a moment, then put it on. It was very short and baggy on his frame and it smelled like grease, but it felt like Sans. It gave him the determination to continue on.

.

.


So just to be clear, Frisk and Sans didn't do a full 'fusion' as some of you had been expecting, though That AU is definitely still on the table considering the nature of this tale. ;P Instead, Frisk had gained the ability to access a small fraction of Sans' skills which may or may not be limited to seeing shortcuts. Sans arguably got the better end of the soul-stick as he now has increased magical potency, though perhaps that will come at a cost? We shall see!

Next Chapter up tomorrow morning!