(I'm a huge fan of AU's, but usually they just simmer quietly in my head. This one was insistent enough that I did something with it, however. Frisk never left the ruins in this one, and got to stay safe with Toriel. This Frisk is gender neutral and on the autism spectrum. That last one in particular is very special to me.)
"Frisk, Darling, be a dear and take the pot of snails off the heat?"
The small child nodded seriously, carefully gripping the heavy pot with both hands as they carried it off the stove towards the bench. A big hand stroked them on the head as they did so.
"Thank you, dear. I'll shell these for the pie, you go finish up the schoolwork I gave you. If you finish the snail pie there's ice cream for dessert."
Toriel turned back towards her work as the child skipped off, humming in quiet contentment.
Unseen, Frisk grimaced at the thought of the snail pie, the promise of Toriels excellent icecream the only reason their plate would be cleared this evening. Picking up the workbook she had made for them, they began working on their multiplication tables, sprawled out in front of a warm, flickering fire.
It had been 3 months since their crash landing into the underground, and already their memories of the overworld were fading. They didn't miss them. They remembered the darkness of the cellar, the pain, the loud screaming that hurt their sensitive ears. No, there was nothing above ground for them. Here there was warm light and good food, and a mother figure who understood that Frisk sometimes needed to rock back and forth when they were overwhelmed.
While they chewed their pencil and contemplated the knotty question of 6 times 15, one hand brushed a burn on their arm unbidden.
Mama Toriel wasn't completely safe.
Not if they went near the door.
They didn't hate her for it. They had seen the pain and fear in her face as Frisk had tried to leave. It had been hard to miss, even for them. Frisk had pulled their soul close to them and fled the battle, fled the burning pellets as they sobbed, and Toriel had hugged them close and gently taken them upstairs. She had said the underground was dangerous for children, and the memory of a golden, sneering face rose in their mind. They shivered despite the warmth. There were dangers down here, too, smiling faces with emptiness behind them and whirling pellets that first entranced, then hurt bad enough to bring darkness floating on the edge of their vision...
Best to stay close to her, in the ruins of Home.
"Dinnertime, Frisk!"
The child pulled a face, the thought of the icecream to come filling them with Determination.
…
"-where, oh where could fluffy bunny be? Peekaboo!" Frisk giggled as the cardboard rabbit popped up on the last page and Toriel gently booped their nose. "Alright, you brushed your teeth?"
Nod.
"Washed behind your ears?"
Nod.
"Good child." The covers were gently tucked in and Toriel gave her adopted child a fuzzy kiss on the head. "Goodnight, Frisk. Sleep well."
Warm darkness folded over them as the light was clicked out, Toriels soft pawsteps fading into the hallway. Quietly, Frisk waited until the light in Toriels bedroom went out, and loud rumbly snores began to echo through the house. They'd been waiting for a while, ever since they had first noticed Toriel sneak down to the basement. She would always return smiling. Frisks curiosity couldn't take it any more. They had to know.
It was just a peek. It wasn't like they were leaving, after all. Toriel would never have to know, it was OK. Right?
Right?
No matter. They had to find out.
Padding out carefully in thick slippers, they crept down the hall, ears tuned for any change in Toriels breathing.
All clear.
Now that they were facing the basement, they were wondering if maybe it was such a good idea. The stairwell was a deep and gloomy black, a hole into a potentially dangerous place. Creeping down the pitch black stairs, they steeled themselves and raised their hands, focusing hard. A wavering magical light crept over their fingers. Toriel had done her best to teach Frisk the basics of magic, but for some humans there was only so much they could learn. Monsters had always found it easier, and weeks of practice had left Frisk only able to summon a tiny light source.
Right now, it was enough. Even then, the warping and flickering of the light made the shadows grow and change and shift, now a harmless corner, now a creeping, grasping monster. Heart banging in their chest, they pressed on, legs quaking in fear.
They passed an archway, facing down a long, seemingly endless corridor. Summoning the last of their strength, they tiptoed down, light flickering and fading as they grew tired and scared.
It was never going to end.
They were going to die down here, alone in the dark.
BOM.
Clutching their nose, Frisk fell back sharply, the light snuffed out as they had collided with the door.
Darkness swallowed them. They began to rock and flap, something that usually calmed them but now just barely kept the fear at bay. It was so dark. As they gulped air, ready to scream for Toriel, a noise from the door froze them solid.
The crunch of snow.
Slowly it drew near, the beating of Frisks heart almost painful now as icy horror crept through their veins.
The noise drew close to the door. And stopped.
There was silence.
Then:
"Hey there, ma'am, whadda you think of this one? I think you'll love it. What do skeletons say before they eat dinner? Bone appetit!" It was a big, calm, sleepy voice, like if a tired dog could speak. Frisk couldn't help it. They giggled softly.
Silence fell like an axe.
"You aren't the lady...who are you? Who's there?"
Frisk clapped a hand over their mouth and whimpered. The slow voice had suddenly hardened.
"Answer me!"
Frisk swallowed. They never usually talked, but there was nothing for it.
"M-" They swallowed again, throat dry. "My name is...Frisk." The darkness seemed to swallow their hushed words. "I...live here..."
"Frisk...that isn't a monster name...what kind of monster are you?"
"I'm...not a...I'm human..."
"A human? Have you hurt her? So help me, if you have..."
"No! No I live with her! She makes me pies, please don't be mad!"
There was silence, then a deep sigh.
"Ahh jeez, lady...what have you gotten yourself into...?" There was the sound of a throat being cleared, an odd rattly noise. "So...a human, huh? Can't say I see many of those around here. They don't...well...if they do get down here, they don't last long."
"The lady says the underworld is dangerous...is it really?"
"You have no idea, kid. She ain't just saying that to keep you here. This place would eat you alive, sweety."
Frisk sat down next to the door and crossed their legs. Talking to this stranger helped distract them from the dark.
"How's it dangerous? She won't say."
"Oh theres lots of dangers. Just within the next few miles theres my brother. A human hunting fanatic if I ever saw one. Hmm, nah, I tell a lie. Can I ask you something, kid?"
"Only if you let me do the same." They smiled. The voice was talking of the dangers awaiting them, but at the same time, they felt safe. The voice was rich and calming.
"Ok, I need you to keep this under wraps. See..." There was a pause, like someone quickly looking over their shoulder. "My brother...he's too gentle for his own good. Couldn't hurt a whimsun. He'd probably just make friends with you. He thinks he's a scarier guy then he is. I just let him dream. Doesn't hurt no one and he has fun with it. Now, Undyne...she'd kill you without a second thought. Stone cold killer, that one. Now, what did you want to ask, kid? Keep in mind, I don't usually make promises."
"Please don't tell her I was here. She'd be upset with me. Are you her friend?"
"Eh, that promise doesn't require effort on my part, that's easy enough. Jaws are sealed, kid. And yeah, we are friends. I think. We tell each other jokes through the door."
"Can't you come in?"
"Can't leave my post, buddy. Besides, I have orders. The moment I clap eyes on a human, I have to take them in. If I saw you, kid, I'd have to kill you."
Frisk chuckled.
"Don't be silly, Mr! You're too nice! I like you!"
There was silence, then an eerie chuckle.
"'Nice?' You really think I'm 'nice'? Oh sweety, I'm not nice at all."
"But, but you're friendly...and funny..."
Frisks heart rate began to increase. That voice didn't sound too good.
"You'd be eaten alive out here, kid. That lady you stay with, she isn't like us. This is the UNDERWORLD, Frisk. There's worse things here then just Moldsmals. There's monsters you can never imagine hiding in the shadows. You think I'm nice? If that door wasn't there, Frisk, you wouldn't be thinking that." The voice was getting closer, as if the person behind the door was leaning forward. When they spoke, it was as though they were whispering straight into Frisks ear.
"THERE'S WORSE THINGS HERE THEN THE BIG BAD WOLF."
Frisks legs acted as if on their own accord, sprinting down the dark corridor as though the monster behind the door was right behind them. Their breath was ragged in their throat as they slammed against walls in their panic, before mercifully tripping over the bottom of the stairs, scrambling up them on all fours before running as fast as they dared to the safety of their room.
The darkness in their room seemed a friendlier sort, less choking fingers and more a warm and reassuring hug as they shook under the blankets, body aching where they had run into walls. Slowly the trembling eased as they flicked their fingers, stimming desperately. In the morning they would tell Toriel the bruises were from falling out of bed. Toriel would never have to know about this.
And Frisk would never go down there again.
…
Leaning his head against the door, Sans sighed gently to himself. He felt bad about that. Truth be told, he had a good feeling about that kid. They'd seemed genuinely nice. He hadn't wanted to scare them, but nor did he want to see them impaled on Undynes spear. A brutal end, especially for someone so young.
He shrugged and began to plod his way back to his post. Well, whatever the ethical questions, at least that one was safe.
In the distance her heard his brother yelling loudly at something. He's probably mistaken the lesser dog for a human.
Again.
Chuckling, he sat back down at his post, pulling his hood over his eye sockets.
"I kept my promise, lady. I kept them safe."