Welcome to a new fanfic! I've been COMPLETELY obsessed with Undertale lately, but I still can't shake Harry Potter, so... This was born! I have a little info ahead that might be important to know later in the story.

MONSTER AGING:

For the first part of their life, CHILDHOOD, monsters will age twice as slow as humans, so every 2 years for humans is 1 monster year. This period takes between 10 to 12 monster years, or 20 to 25 human years.

The second part of their life, PUBERTY, starts after child monsters have 'popped' and goes until adulthood. In this faze, they age five times as slow, meaning that every 5 human years equals 1 monster year. This period is about 10 or 11 monster years long, or 50 to 55 human years.

This means a monster is between 70 and 80 years old when reaching ADULTHOOD. From there on out, they will age ten times as slow, meaning that for every monster year, 10 human years go by, or for every 10 monster years, 100 human years.

Once reaching ADULTHOOD, Boss Monsters stop aging until they have kids, like Gerson tells Frisk in the game. In this story, not only the Dreemurs are Boss Monsters, but also the skelebros, Undyne and Gerson himself. Gerson is old because he used to have a kid himself (he's Undyne's grandfather) but his daughter died.

"Lily, take Harry and run! It's him! Go! Run! I'll hold him off!"

…

"No, please! Not Harry! Kill me, but let him live!"

"What are you? You're a monster! You and your half-blood child will die tonight, creature! Avada Kedavra!"

"The world will be off better without freaks like you. Avada Kedavra!"

. . . . .

Harry groaned softly and curled into himself, trying to fight off the pain in his body. Sadly, it only got worse with movement. He whimpered softly and took a few gasping breaths. Tears were streaming down his face, wetting the golden flowers underneath him. He was pretty sure that he had broken a few ribs at least. He was going to die down there, all alone, just like he deserved. Freaks didn't deserve love, after all.

He didn't hear the soft sound of footsteps and rustling of clothes over his own weak sobs and cries. Only when someone knelt down beside him, did the young boy realize he was no longer alone. The boy tensed up as a large, fluffy hand rested on his head and gently stroked his hair out of his face. Harry blinked his big green eyes up at the person and gasped when he saw she wasn't human.

"Do not be afraid, my child," the woman spoke gently, smiling softly down at him.
"I am Toriel, caretakers of these Ruins. I will take good care of you at my home."

The young boy was shaking like a leaf, but he still nodded his head quietly. She seemed nice enough. Maybe… maybe she could help him get better again before she realized he was a freak and send him away. It might be a bit unfair, but if it could save him, he was willing to take the chance. Besides, he'd leave her alone again soon enough. No need to bother her for longer than he had to.

Toriel smiled comfortingly at him as she lifted him into her arms. The shift made Harry groan and whimper in pain, but that resided somewhat again as he coddled into the woman's warm body. His eyes slowly fell closed as Toriel hummed a soothing tune under her breath and before he knew it, he had fallen sound asleep in her arms.

. . . . .

When Harry woke up again, he was lying in a soft bed. The young boy scowled confused at this. How did he end up in a soft bed? He slept in a cupboard and on his family's holiday in California, he had slept on the ground. There had been a relatively comfortable rug in the room, so it wasn't all that bad…

His eyes went wide in horror as he remembered what had happened and he shot up straight in the bed. His sides gave a very painful tug, making him groan softly as he pressed a hand against his ribs. He noticed that the fabric under his hand was much softer and thicker than the flimsy, grey, oversized shirt from when he arrived there. Instead, he was wearing nice blue flannel pajamas. They were still a few sizes too big, but at least they looked better than Dudley's old clothes. Harry felt a pang of guilt for taking advantage of the nice goat lady like this. No… he was sure that part was only a dream. It had to have been a human that found him.

Slowly and carefully not to hurt himself more, Harry slid out of the bed. The room he was in looked really nice. And so big too! it had to be about as big as Dudley's! There was even a box full of toys and more clothes in the wardrobe. All different sizes too, just like the box full of shoes. Harry wondered if the lady had a child herself and if he was now using their room. He hoped not. He didn't want to intrude on a family like that.

After inspecting everything, Harry walked over to the door and stepped out into the hall. On the left from his room were two more doors while on the right, he could see stairs going to some sort of basement and the front door and another open door. He could smell something really nice in there, so he decided to follow his nose and curiosity.

He entered a small living area, with a table, a bookcase and a large brown armchair where Toriel was seated. For a few moments, Harry couldn't keep his eyes off the woman. She really was a goat lady! So it hadn't been a dream after all. This had to be the weirdest thing he'd ever come across. He jumped a little when Toriel spotted him and put her book down.

"Oh! You're awake I see!" she greeted him cheerfully.

Harry bit his lip cutely and nodded. He was still terrified. Would she be angry he had overslept? Would she want him to leave right away? He didn't want to be a bother to her, but this home looked really nice, so he didn't really want to leave yet. The kind woman didn't seem to notice Harry's fear as she got up from her seat and ruffled Harry's hair playfully.

"You must be so hungry, my child!" she said cheerfully.
"Not to worry, my dear. I have just what you need. Come along now."

In the kitchen, a large stack of pancakes was waiting for him, which Toriel put on the table, along with syrup and a plate. She waited until the boy had clambered on the chair before pressing a soft kiss on his forehead and walking back to her own seat. Harry stared and scowled.

"U-uh… Are-aren't you going to eat too, miss Toriel?" he asked shyly.

"Not to worry, dear child," the woman chuckled, looking back over at him.
"I already ate two hours ago. You can eat as many pancakes as you like."

Harry blushed and looked down. How long had he been asleep that miss Toriel had already eaten? Wasn't she angry at him? She probably was, but she didn't show it because she was such a nice person. Too nice to someone like him.

"I'm sorry," he mumbled ashamed.

"For what?" Toriel asked amused.
"You were very injured. Of course you needed a lot of rest."

Harry's blush brightened even more and he quickly turned his attention on the pancakes in front of him. Even though Toriel had told him he could have as many as he wanted, he only ate one. it was definitely delicious, but he didn't dare take more. Toriel was just being polite, after all. He should do the same for her and not be a burden.

"Done already?" Toriel asked surprised.

Harry nodded his head and looked down at the floor.

"In that case. Why don't you go get dressed and play in your room for a bit?" Toriel suggested.
"Oh! And would you mind telling me your name, dear child? I would have asked earlier, but you weren't in any state to reply then."

Harry felt tears well up in his eyes, but quickly blinked them away. Boys don't cry. That's what uncle Vernon always told him before hitting him in the face to make him stop crying. It never worked, but Harry was smart enough to avoid crying as much as possible.

"I'm Harry Potter," he whispered quietly.

"Well, Harry. I'm very happy to have you live with me!" Toriel said smiling.

Again he nodded and hurried out the door. Toriel was angry at him for having to take care of him. no matter how hard he tried, he'd be a burden to her anyway, wouldn't he? How stupid of him to think a freak like him could ever be anything but a bother to other people.

Since he couldn't find his own clothes anymore, Harry picked out a shirt and pants from the wardrobe that were closest to his own size. It was a purple shirt with black stripes and it was only a little bit big on him. The same with the black pants. Harry smiled. He was happy to get to wear such nice clothes.

. . . . .

Toriel walked into his room a few hours later to announce lunch, smiling softly as Harry was playing with the old toys in the box. His bed was neatly made up already, done by the boy himself, and all the toys he didn't play with were all still neatly stored away.

"Are you hungry, my child?" Toriel asked.

Harry looked up bewildered and hurried to put the toys back in the box, fearing retribution if he left a mess. Toriel smiled softly, thinking that Harry's hurry was his eagerness to get food. The rest of the day went by very quick as Harry slowly started to relax more around Toriel. He was still jumpy and expected to be met with cruelty and violence when he did something wrong, but at least he started to smile and hope again.

So, when Toriel took him to the room to tuck him in, he made his very first mistake. He asked a question.

"Miss Toriel. Do you have any children?" he asked softly as he sat down on the bed.

The goat woman tensed at the question, her eyes widening in shock before dulling. In his worry for the nice lady's wellbeing, Harry made his second mistake. He didn't stop with one question.

"Miss Toriel?" he asked worried.
"Did I say something wrong? Are you ok?"

"I'm fine, Harry," she mumbled, harsher than he had heard her speak so far, making him tense.
"Go to sleep, my child. This is no time to start asking such questions, alright?"

Harry looked down ashamed and nodded his head. He didn't look back up until the door closed behind Toriel. With a sigh, he turned around in the bed so he was facing the wall and closed his eyes.

He dreamed about Toriel, yelling at him for being a bothersome, nosy freak. For not telling her how worthless he was before taking him in, for abusing her kindness and being a burden. He woke back up in the middle of the night with tears in his eyes.

Gasping for breath, Harry rubbed his eyes, only to feel his fingers on one hand were oddly hard. His eyes widened in horror and he looked down at his right hand. Three fingers had lost their skin, leaving only bones to be seen.

"No," he whimpered terrified.
"Nonononono. Not now, please!"

. . . . .

Harry was very lucky that his hand was back to normal by the next morning, but the damage had been done. He was withdrawn and fearful, so much so that Toriel was getting very worried.

Harry reminded her a little of Chara when she had first arrived, but they used to have Asriel to help them get over their fears and become comfortable with living in the Underground. All Toriel could really do was try her best to let Harry know that he was welcome with her and even wanted. She would show him love.

It was a very slow progress, but by the end of the week, the young boy dared to talk again. He kept anxiously offering to do chores, but Toriel insisted on doing them herself, so Harry spend most his time in his room, playing with his toys when she was busy. Otherwise, he would sit next to the fireplace and listen to her while she read to him.

Again, Harry started feeling comfortable with her and after ten days, he started accepting that maybe, she wouldn't send him away the moment he tripped up. That, was perhaps his biggest mistake of all…

. . . . .

Harry had been playing outside when his hands started itching terribly. He started scratching absentmindedly until there was a soft ripping sound and a stinging pain from his right wrist. Harry looked down in horror to find his skin was literally peeling off like it was nothing. He shouted and stumbled back as more tiny flecks of skin fell off by themselves, revealing bone and muscle. The sight almost made him sick to the stomach.

He tried to rub himself clean, do something, but to his bewilderment, he found he was only making it worse as now his other hand also started to flake off. Was he going to end up falling apart? He didn't want to die yet! He was only eight. He had a whole life still in front of him, no matter how useless and miserable it would be. He wasn't ready yet. He wanted to find a place even someone like he could be happy and call it home.

"Harry?!"

In a fit of panic, the boy stuffed his ruined hands in his pockets and watched bewildered as Toriel approached. She couldn't see what was happening. She'd never let him stay after that. Too terrified that she'd find the dead skin lying on the ground, he rushed forward and met her near the door of her home. The woman had been smiling, but as she saw Harry's petrified expression, she frowned.

"Are you alright, my child?" she asked worried.
"You are awfully pale. Are you getting sick?"

Harry swallowed and shook his head hurriedly. He didn't want her to be worried because of him. he was already causing her more than enough trouble as it was. Toriel sighed and dropped it, knowing that Harry wouldn't tell her even if he was getting sick, which reminded her of other things she had been wondering about for a while now.

"Harry… I tried not to be too curious, but if you don't mind, could you tell me how you got that odd scar on your forehead?" she asked.

Harry had to resisted the urge to put a hand over the scar and looked down, like he so often did.

"I-it's… from a-a car crash," he muttered softly.
"I d-don't r-remember it, b-but aunt Petunia says my parents died in it…"

"Oh, you poor sweetheart," Toriel murmured, leaning down to hug Harry and kiss his forehead, right over the scar.

Harry shivered a little and took a step back as soon as he was let go of. Hugs still made him nervous. He wasn't used to touches not hurting. Toriel sighed sadly and stood back up, still looking just as worried as before if not more.

"What about the other ones? The scars on your back and arms? And the ones on your legs?" she asked.

Harry tensed. He couldn't tell her. If he told her it were punishments for freakishness, she'd be angry, wouldn't she? After all, no one would want a freak in the house. His eyes watered and Harry hunched his shoulders while looking pitifully up at Toriel.

"I-I'm so sorry, miss Toriel," he sobbed before running off into the house.

He could hear the goat woman call his name, but he ignored it in favor of closing and locking his – no, Toriel's – door and hiding under the sheets of his bed – Toriel's bed because nothing in this house was his. Not even the clothes he was wearing.

. . . . .

Harry couldn't sleep at all that night. He was terrified that Toriel would burst into the room and kick him out of the house, or that more of his skin would fall off if he closed his eyes. It still didn't change the fact that his face started itching horribly, but he resisted the urge to scratch for as long as he could.

In the end, he couldn't resist the need for relief and he scratched. To his horror, a whole patch of skin loosened from his cheek and fell on the bed with a disgusting wet slap. The boy gagged and jumped out of bed, feeling dizzy and sick. It was a good thing the room was so dark at the moment, otherwise he would definitely have thrown up at the sight of.

Shivering in fear, Harry stood there for a few moments before making up his mind. He couldn't stay there. If Toriel saw what was happening to him… No. He couldn't let her know. It would break his heart to see her reaction of what Harry was becoming. Really, it would be best for everyone if he just left and never returned. She'd be happier without him there, he was sure.

Determined, Harry walked over to the closet and pulled out a jacket. It wasn't very thick, but it was summer in the middle of California. He'd be fine, even this deep underground it wasn't that cold. He wanted to take a scarf too, but decided against it at the last minute. He was already taking clothes that weren't his. He shouldn't steal everything Toriel had left here out of kindness.

He put on some shoes, the only ones in the big box of them that fit him, and he snuck out of the room. Just as he had hoped, Toriel was still sound asleep, giving him the chance to creep through the hallway towards the front door. There had to be a way out of the Ruins somewhere, but Harry had already been everywhere together with Toriel and he hadn't seen one…

Harry took a step back from the door and he looked over at the staircase. It was the one place in the house and the Ruins he wasn't allowed to go. Well… that and the room between his and miss Toriel's room – both were miss Toriel's room. Harry didn't belong here, he was a freak – which was always closed for some reason Harry hadn't dared to ask.

As he went down the stairs, Harry was careful not to make any noise and before long, he was standing in a long, dark hallway. Harry frowned. This looked nothing like what a basement should look like… Curiously, he followed the hall, which made a turn halfway before he came to a halt in front of a giant purple door. Harry blinked a few times in confusion before stepping forward carefully. Perhaps this was the way out.

The door opened with a little effort, making Harry smile relieved as he stepped out into… yet another long, dark corridor. Where would it end? Was it going to be just like this all the way up to the surface?

His eye itched, and without thinking, Harry lifted his glasses off with a bony hand to rub it. A wet squelch, and a momentary loss of sight from his right eye had the boy tense in horror. Slowly, he brought his hand down again, blinking heavily until the sight came back to his eye, sharper than before even without his glasses. It enabled him to properly see what was now laying in his hand.

Harry fell forward on his knees, gagging heavily before throwing up in disgust. It was his eye. His eye had come out together with his eyelid. It was by far the most horrifying thing he'd ever seen, and he'd once accidentally walked in on his uncle showering without closing the curtain.

A loud, horrified wail tore from his throat and Harry sat there for the longest time, sobbing and gagging. He threw up two more times before he was able to pull himself up on shaky legs and started walking again. He needed to be gone before Toriel found anything.

Maybe his relatives had been right to leave him behind. He was literally falling apart, how disgusted they must have been with him…

He walked for several minutes before he came across another door. Yet again, he pushed it open, unsure what he was going to find on the other side. He hoped it wasn't another corridor. He hoped he would find his way out of the mountain soon.

Whatever Harry had expected, it was not the gust of freezing wind and the soft crunching of snow underneath his feet at the first step out. He looked up in wonder, being even more shocked to find a perfectly closed off cave ceiling high over his head. It was lighter out here as it had been in the Ruins, but still relatively dark for a place that had no sunlight. Harry wondered how there was light at all, since he couldn't see where it was coming from.

Shrugging the strangeness of this place off, Harry continued his trudge through the thick snow. He was starting to regret not brining that scarf now…

. . . . .

Toriel was in a panic when she woke up in the morning to find the human child gone. A whole patch of skin was all that was left on the bed as proof that Harry Potter had been with her for a little over a week. Half of the boy's cheek, if her human anatomy was correct. It was strange though. She knew some monsters that shed their skin while aging, but she was very certain that humans did not do such a thing. Still, the skin was clearly dead and dry.

With a sigh, she sat down and buried her face in her hands. Yet another human had gone to meet their doom. That would make a full seven now. At least now, Monsters could finally be freed. But at what cost would their freedom come?