UltSans hesitated, his steps faltering as he stopped once again. His breathing was shallow, erratic—faster than before.
He could feel it—the trembling in his bones, the tightness in his chest.
Anxiety.
Even after everything he had done over the resets—after all the killing, after all the suffering, after all the "necessary" actions he had forced himself to take—he still couldn't relax.
He kept trying to wipe away the tears, trying to suppress the overwhelming sadness that threatened to drown him whole.
But he couldn't.
UltSans:"This is... just getting weirder... Kiddo, what is going on with me?"
He expected Chara to answer.
For her voice to cut through the silence, sharp and unyielding like always.
But instead, he heard something else.
Something deep, heavy, foreign.
Abyss: "Maybe resting..."
UltSans flinched.
A shiver ran down his spine, and he instinctively looked around. His nerves flickered with alarm. No one was there.
And yet, someone had just spoken to him.
His breath hitched. Was he hearing things?
Then—movement.
The inky black mass that had been fused into his back began to shift.
The tendrils along his shoulders peeled away, creeping outward, slithering like a liquid shadow. The entity moved, shifting beside him, hovering just near his head.
For the first time, UltSans truly saw the symbiote that had merged with him.
He jumped slightly, startled, his body jerking as he took a half-step back.
UltSans:"W-what?—U-uhm... I never thought... Seeing hate like this..."
Abyss didn't move, its form barely shifting—just watching. Then, it finally spoke.
Abyss:"I'm not Hate... I absorbed Hate... I'm Abyss."
UltSans blinked. His expression flickered between wary curiosity and uncertainty.
UltSans:"...Ok?... Well... Abyss?..."
He let out a shaky exhale, rubbing the back of his neck.
UltSans:"I guess it's... Darkfull to meet you?..."
He tried to chuckle at his own joke—tried to force a smirk, tried to be himself.
But the sound that left his throat was a pathetic excuse for a laugh—weak, empty, forced.
Abyss stared.
It tilted slightly, studying him with a strange, unreadable stillness.
Abyss:"Good joke. But you've lost your touch, from what I can see."
UltSans let out a dry scoff, shrugging.
UltSans:"Yeah... Well, how do you know if I did or not? You don't know me."
Abyss didn't hesitate.
Abyss:"I don't know you. But I have seen enough to know you."
UltSans narrowed his eyes slightly, his brow twitching.
UltSans:"... Uhm... That... that sounded weird... You don't... know me, but you also do?"
Abyss:"Yes. I don't and do. But you don't know me."
UltSans exhaled sharply, pressing his fingers to his temple.
UltSans:"Alright, brain melt... Let's rewind a bit. How do you 'know' me? I mean... How did you... see all about me?"
Abyss remained eerily still for a moment.
Then, it finally answered.
Abyss:"I saw your memories... We are both anomalies. Experiments. We both shouldn't exist, but we do."
UltSans' expression darkened slightly.
Abyss:"I complement you... Improve you... Heal you..."
UltSans' fingers twitched.
Abyss:"You complement me... Evolve me... And allow me to be more than alive."
The words settled in the air, sinking deep into UltSans' mind.
He swallowed, shifting his weight.
UltSans:"...Alright? I guess that's... good?"
Abyss didn't respond immediately.
It simply watched.
And in that moment, UltSans realized something.
This wasn't just some mindless parasite.
Abyss had already begun understanding him.
And that was far more unnerving than anything else.
UltSans moved slowly, his steps measured, careful. His shoulders felt heavier than usual, weighed down by something unseen—or perhaps, something deeply felt.
For a moment, he considered what Abyss had said.
But the exhaustion clinging to his bones, the sharp edge of unease scraping at the back of his mind, made it impossible to settle.
UltSans:"I don't think I can sleep after all of this. So… I don't know."
Abyss shifted slightly, its fluid form hovering just beside him.
Abyss:"You will sleep, but your mind refuses. Stop being nervous, and you'll sleep."
UltSans let out a dry, humorless scoff.
UltSans:"And what makes you think I want to sleep? I can't sleep where I'm not used to be."
Abyss didn't hesitate.
Abyss:"Because you don't feel safe, but taken from where you feel you deserve to be."
UltSans stopped.
Slowly, he turned to face Abyss.
His stare was cold, empty—serious in a way that left no room for laughter.
Tears threatened to rise, but he refused to let them fall. He wouldn't allow it. Not now.
Not anymore.
UltSans:"You mean I… deserved to be in Hell?"
Abyss hesitated.
It had observed everything UltSans had been through—his endless resets, his massacres, the weight of his choices. But it had also seen the reasoning behind them, the purpose.
It had seen the shattered pieces of someone who once wanted to believe in better things.
And now, standing here, UltSans was waiting for an answer.
Abyss chose its words carefully.
Abyss:"No. You didn't. That was coincidence. But your body did… not your soul."
UltSans' expression flickered, his breath hitching for half a second.
Then, he let out a deep, half-growl, half-sigh.
Something between exasperation and bitterness.
Without another word, he turned away and continued walking.
Abyss didn't press the conversation further.
It simply followed.
UltSans continued forward, his posture tense, his mind caught in the haze of conflicting emotions. The symbiote hesitated for a brief moment, its shifting, inky form lingering outside before it slowly melded back into his body, retreating into the depths of his being.
The hallway ahead remained silent, save for the faint hum of machinery echoing from the deeper levels of the Institute.
After a moment, he stepped into the elevator, pressing a button to descend further into the unknown.
The space inside was dimly lit, the flickering fluorescent light above casting his shadow in broken intervals against the steel walls.
As the elevator moved downward, he hesitated.
Then, almost absentmindedly, he whispered—his voice taking on a soft, almost haunting singing tone.
UltSans:"...I'll maaaaake, youuuu saaaaayy, hooowww prooouuud... You, aaare of meee, so, pleeease, ssstaaaay, aaaawaaaaaake, juuuust looooong, eeeenough to seeee, myyy waaaaaaay... My, waaaaay..."
The melody faded into silence, lingering like a ghost in the stagnant air.
A sigh escaped him. His fingers flexed slightly before he clenched them into a loose fist.
UltSans:"...Focus, Sans... Focus... It's the humans' fault... It has to be done..."
Abyss had remained quiet, listening.
But something about UltSans' song stirred something within it.
Not confusion.
Not logic.
Something… deeper.
It didn't have words for it, not yet.
But it knew that whatever that song was, it wasn't meant for just anyone.
Abyss:"...You sing... but you carry no joy in it."
UltSans blinked, startled by the sudden remark.
UltSans:"What?"
Abyss didn't repeat itself.
It simply lingered in thought, remaining silent as the elevator slowed to a stop.
A dull chime echoed, and the elevator doors slid open.
What lay before them was not what UltSans had expected.
An endlessly stretching hallway—grotesque, unholy, a corridor drenched in death.
Blood.
Bones.
Skeletons scattered across the floor, some half-buried in the strange dark substance clinging to the walls. The entire corridor seemed wrong, like something had taken over this part of the facility and warped it into something else entirely.
The black organic mass pulsed faintly along the walls, writhing in places like living veins, spreading across the metal panels.
UltSans' breath hitched as he hesitated.
He lifted his right hand, opening his palm fully.
The small flame hovering above his hand grew, its glow expanding, pushing back the suffocating darkness with its flickering warmth.
The hallway stretched forward into the abyss.
And he had no choice but to enter.
With caution, he stepped inside, his steps slow and deliberate, doing his best not to touch the strange black material.
But then—
His foot landed directly onto it.
The moment his sole pressed into the strange substance, a sharp, unnatural chill surged through his spine.
Something wasn't right.
Abyss emerged instantly, peeling out from UltSans' back, its shifting form coiling beside him.
Abyss:"Do you seriously find this gross?"
UltSans jerked slightly, his body shuddering.
UltSans:"Yes! Got any problems?!"
Abyss hesitated.
Then, it looked around, taking in the scene.
Abyss:"Yes. Because that makes it seem like you also find me gross."
UltSans froze.
Then, with exaggerated movement, he shook his head widely, his mouth half open in dramatic disbelief.
UltSans:"But I don't even know what you are?! I thought you were Hate, something already inside me! So I don't find you gross because you're already inside me!..."
He suddenly stopped.
His face twitched.
UltSans:"...And that sounds very weird."
Abyss let out a faint, distorted chuckle.
Then—
Abyss:"Well... I'm a symbiote. And what you just called 'gross'... is made by symbiotes. It's part of them. Part of other symbiotes."
UltSans' eye sockets narrowed slightly.
UltSans:"...What does that even mean?... What is a symbiote?..."
Abyss paused.
Then, slowly, it began to explain.
Abyss shifted, its tendrils curling slightly as it processed how to explain.
Abyss:"Symbiotes... we are a species. A lifeform that bonds with hosts, fusing with them to create something more."
UltSans listened, his glowing blue eyes narrowed slightly.
Abyss:"Alone, we are incomplete. We do not have true shape or structure. We do not have stability. We need a host to define us—to become something greater than a formless parasite."
UltSans tilted his head slightly.
UltSans:"So, you're a body snatcher?"
Abyss didn't react to the accusation.
Abyss:"That is what we are perceived as. But not all symbiotes take control. Some... merge. Some become something more with their hosts. A perfect union. An evolution."
UltSans hummed slightly, digesting the information.
UltSans:"And this hallway? This... mess?"
Abyss shifted its gaze toward the grotesque corridor, its glowing red veins pulsing faintly.
Abyss:"This is what happens when symbiotes are left unchecked. Some symbiotes lose themselves—mindless, without a host to keep them stable. Others... are abandoned. Pieces of them remain, growing, spreading. It is the remnants of symbiotes that were either destroyed or left to rot."
UltSans' stomach twisted slightly.
UltSans:"...So what you're saying is—I'm walking through a graveyard?"
Abyss paused for a moment.
Then, it spoke.
Abyss:"...No. A graveyard is a place where the dead remain dead."
It glanced at the dark, writhing mass crawling across the walls.
Abyss:"This? This is still alive."
UltSans' grip on his flame tightened.
And slowly—he stepped forward.
Deeper into the unknown.