The House of Undertale AUs

Chapter 2: Gaster and Core Frisk

Y/N's POV:

Gaster frowned at me, putting down his test tubes. "You used my full name," he said in that weird language of his. "So you must really need my help."

"I do," I responded, choosing my words carefully. Slowly, I told him all about what Ink told me and how I had to do something about it. Gaster, unfortunately, doesn't want to do anything.

"Waste of my time," he grumbled and turned back to his experiment. My temper instantly rose up but I fought it down.

"Waste of your time," I repeated, trying to keep calm. "But if I don't do anything, my sister might die."

"So?" Gaster said calmly. I took a deep breath, but I really hope that saying, "Calm before the storm".

"So... that means I need your help and your cooperation.

He ignored me completely. I clenched my hands into fists. "Don't you care about the monsters living there?" I asked, my anger rising like a bullet. He shrugged and I absolutely lost control.

"SO YOU DON'T CARE ABOUT YOUR SONS EITHER?!" I shrieked. Then, I slapped my hand over my mouth. I just played my red card. It felt like time froze as Gaster slowly turned around.

"What... did you just say?" He asked, his eyes glowing a deadly yellow and blue. I gulped, wondering if Gaster would kill me.

Then, of course, fate has to mess things up with whatever's happening. A grey portal opened from a side wall and someone grey stepped through it. My breath got caught in my throat. It was a grey version of Frisk, my younger sister.

"Hi, Y/N," she said. She had two black holes where her eyes were supposed to be at. Her colorful blue and purple striped sweater was now dull and grey (ok, you know the drill. Look at the picture).

"F-Frisk?" I asked, taking a step towards her. There was feeling inside me that she wasn't really my sister, but yet my sister at the same time.

"My name is Core Frisk," she said. "I'm just like Gaster. I can go through time and space. And just like Ink, who you just saw, I can go and see each and every timeline and AUs."

She now faced Gaster. "Your sons, Sans and Papyrus are in danger of getting killed. Do you want that to happen?" Gaster stared at her for a while before shaking his head slowly. "Good," Frisk, well, Core Frisk said in relief.

"Gaster, you know what to do," Core Frisk said before making a portal once again. "And Y/N." Core Frisk hesitated before continuing. "You will soon know the consequences. Be sure to be safe."

And on that happy note, she left me and Gaster alone.

I turned towards him, a frown on my face and my arms crossed. "What is Core Frisk talking about?" I asked. Gaster, for the first time, looked nervous.

"Core Frisk was talking about how I have to merge with you," Gaster said. "It has been done but... it takes a lot of strength and courage to keep a person—no skeleton—like me to keep my powers in check."

"I can do that," I insisted. "It sounds easy." Gaster looked at me but then, he looked away again.

"I told myself to never do that though," he whispered. "It's too dangerous."

"I can do it!" I shouted. He looked at me and I looked directly at his eyes. He frowned, but then came to a conclusion.

"Alright then. Let's do this."

And since it's way too short to end, let's go over to Frisk's POV for once.

Frisk's POV:

I really missed the mortal world but I liked it here. I met a friend when I fell from the hole on Mt. Ebott. His name was Chara. At first, he was a ghost but he accompanied me the whole way. I soon met the skelebros, Sans and Papyrus, and met more monsters that became my friends. Undyne, Alphys, Mettaton, Toriel who became my mother, Asgore who became my father since him and Toriel made up, and Asriel who before was Flowey. Chara, who somehow became more human, not a ghost, and Asriel became sort of my brothers but that didn't stop me from liking one of them.

Chara.

He was so helpful and kind. Asriel was cool but Chara liked stuff that I liked. We both loved chocolate and we liked to play some tricks on Asriel. Of course, Asriel didn't mind but we kind of annoyed him a lot.

Then, of course, Ink came.

I was over at the skelebros' house. Papyrus was making me and Chara some spaghetti since Chara didn't want me to be in trouble, or at least that was his excuse. He said it was for "in case someone attacks you." At that, I rolled my eyes. He always called Sans 'smiley trashbag'. Chara really hates him.

My hair was growing a bit long, so I let Sans cut it. Mettaton was also over since Papyrus and Mettaton had a thing going on now.

"Looks good to you, kiddo?" Sans asked once he was finished. I looked at my hair. It was short, exactly how it used to look like before it grew longer.

"Yea!" I said with a grin. "Thanks, Sans."

"Anytime, kiddo," Sans said with a wink. I went off to find Chara while Sans went to check on his brother.

"Hey, Frisk!" Chara greeted me. He was sitting there on the couch in the living room. We could hear Papyrus and Sans talking to each other.

"OH NO!" Papyrus cried. "THE THYME! I SPILLED IT! NOW THIS SPAGHETTI SAUCE IS NO LONGER GREAT LIKE ME, THE GRRRREAT PAPYRUS!

"Don't sweat, bro," Sans' calm voice said. "At least-"

SANS, DON'T," Papyrus said in a warning tone.

"You won't-"

"SANS I SWEAR."

"Have a bad thyme," Sans finished.

"NYAAAAAAAAAAAAAAAAAA!" Papyrus screamed. There was a crash and Sans came running out with Papyrus chasing him. Me and Chara laughed as they ran by.

"Darlings, darlings," Mettaton said in his robotic voice. "Calm down. It was only just a pun. A very bad pun from shorty here."

"Hey!" Sans protested, which was kind of strange since he was taller than me (let's just assume that Sans' height is regular teen height,maybe about 5 feet. Also, he's 13).

"I GUESS YOU'RE RIGHT, METTATON," Papyrus sighed. "BROTHER, YOU ARE SPARED FOR NOW." I thought I heard Sans do a sigh of relief.

"Hey... who's that?" I heard Chara ask. I looked to see where he was pointing to and saw a skeleton that looked exactly like Sans.

"Sans, how are you out there and here at the same time?" I asked. Sans' head popped up from behind the couch.

"What?" he asked and then saw his doppelganger walking around. "That's really strange. I'll go talk to him. If he's me, he'll just be a fun bag of bones."

"SANS, I WILL DISOWN YOU!"

"AKA another smiley trashbag," muttered Chara. Sans' eye glowed blue as he looked at Chara and I shivered with fear. Sans looked at me and the glow faded. I hugged Chara for no reason at all as Sans left.

"Let's see what going on," I pleaded. Chara sighed and we both headed outside.

"What?!" Sans yelled and I jumped in fright. Chara brought out a knife as I hid behind him.

"Sans?" I asked, peeking from Chara. My breath got caught in my throat. There were now three Sans standing there in front of us.

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Hey guys!! It's me again. For the first time in this whole entire story I actually had Sans make a pun or two! Yes!

Anyways, I hope you enjoyed the first two chapters of this fanfic. Man, I'm gonna have a ton of work when the AU part comes. A skele-ton of work. Hehehe, couldn't resist that.

Peace ☮️