Hello there, fellow reader. This chapter is more focused on action than any other chapter I've written, so if you don't like nearly nonstop action, you probably shouldn't read this, but if you're nice, still read it. That's about all I have to say about this chapter... Hope you enjoy!

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The elevator shook slightly as it made its way upwards before slowing to a gentle stop. The doors slid open with little noise. It was silent outside of the elevator, and I stepped out cautiously. The doors closed with a tight click. There was no wind, no sound, nothing. Everything was gray. The walls were gray, the floor was gray, the emptiness was overpowering. I walked down the short hall and took a left. There was another elevator, but it appeared to be broken, or closed.

"This is going to take awhile…" I told myself, recognizing the layout. Farther down I went, going up to a house that was identical to Toriel's. Even the insides were the same, the furniture in the same places, rooms with the same things. The only exception was the amount of golden flowers everywhere.

"Howdy! I'm in the garden. If you have anything you need to get off your chest, please don't hesitate to come. The keys are in the kitchen and the hallway," I read, looking at a note on a padlock connected to a chain roping off the stairs. I stepped over the chain and walked down the stairs. Another cold, long hallway. Another left turn. A right turn and a long hallway. An elevator was at the end of this hallway. I guessed that it connected to the first one at the beginning of the monochromaticity.

"Huh…" The next hall was aglow with a bright light, illuminating the golden tiles and pillars. My footsteps echoed throughout the hall and I slowed to a stop.

"so, you made it…" Directly across from me was a skeleton. A round, hoodie-wearing skeleton.

"Hello Sans." We looked at each other.

"it looks like you managed to get all the way here without killing anyone…" Sans looked out one of the windows.

"Yeah, I'm awesome, aren't I?" We were silent for a moment.

"you know what i'm going to do, don't you?" asked Sans in a whisper. I nodded.

"Basically." Sans looked at me, his left eye flashed red while his right eye disappeared entirely.

"good bye." Four floating skulls appeared and shot out lasers from their mouths. They disappeared and another four appeared to shoot four more lasers. Two massive skulls appeared on either side of me, and blasted even larger lasers. I barely managed to avoid the barrage of lasers. I realized that they were almost identical to the Gaster Blasters that Gaster used, and gritted my teeth.

"i always wondered why people never used their strongest attack first…" said Sans, giving me a wide grin full of teeth. I slowly withdrew my machete and swung it back and forth to look intimidating. I knew he was one of the harder-to-kill monsters down here, but I was trying to not kill anyone.

"I'm sorry." I rushed at Sans, machete held by my side. Sans summoned an army of bones, and flung them at me. I barely registered their existence and kept going.

"what?!" Sans teleported several yards away and looked at me with rage and confusion. I had my eyes on my target and lunged at Sans. He teleported away and blasted me in the face with one of his skull blasters. Nothing happened to me.

"how come you're not affected by my magic?" He asked, narrowing his eyes. I watched Sans' carefully, not responding to his question. We circled each other, knowing that we couldn't hurt the other.

"If you don't stop, Sans, we'll be doing this forever…" I said, spinning my machete around. "If you give up now, everything can go on as normal…"

"normal? what exactly do you think is 'normal'?" asked Sans, firing off a massive wave of bones that were absorbed into my body. I changed each attack into a crystal and dropped it inside my bag.

"Normal, as in, whatever the normal time flow of this universe is supposed to be like before I came here," I answered without hesitating.

"..." Sans was silent, and closed his eyes. "i'm going to give you one chance to prove yourself… from this battle alone, i can tell you're not from this universe at all, maybe not even from this multiverse… so, i'm gonna give you the benefit of doubt… for now…" Sans stood there silently for a minute with his eyes closed.

"Are you waiting for me to kill you or something?" I asked, raising my eyebrow.

"pretty much… i know you're immune to magic, for some reason, so anything i do to you is useless…" said Sans. He stood there for several more minutes before opening his eyes again.

"Did I pass your test?" I asked, smiling.

"yeah... yeah you did, surprisingly… or rather, since you didn't kill anyone, unsurprisingly…" said Sans, stepping aside. "i'll let you pass… as long as you keep your promise to not kill anyone…"

"How do you know about that?" I asked skeptically.

"No one gets past every monster in the Underground, without killing them, by accident," answered Sans. I found that I respected the short, chubby skeleton, and nodded to show my appreciation.

"Thank you," I said, walking past him. "I won't kill anyone." Sans teleported away and left me alone in the massive hall. I sighed in relief and passed through the golden hall, back into the monochromatic halls that were everywhere else. A large doorway and a massive flower garden. A single monster stood with its back to me.

"You actually made it…" the voice of the monster wasn't the same as the "simulations" I had gone through, but perhaps it was just a product of this universe.

"Are you alright?" I asked, unsheathing my machete. I had an uneasy feeling about this monster, and I couldn't pinpoint why, but it worried me.

"No…" The monster turned around to reveal a scarred, skeletal face. "I was starting to get bored! Hello Subject Zero…"

"Gaster… What did you do? I thought you said you were going to wait at the barrier!" I said, clenching my machete tightly.

"Like I said, I was getting bored, and this host seemed to be bored as well, so I gave him a well-deserved nap," answered Gaster, showing off his new body. It was the same as the normal monster that was here, except completely skeletal, and the face had Gaster's signature cracks.

"You're dead to me." I launched the first attack, swinging my machete horizontally across Gaster's body.

"Oh ho ho! Now this is interesting!" Gaster nimbly dodged my blade and launched a massive fireball in my direction. I faced the fireball head on and ran through it. That was the first time that I had felt pain from magic.

"ARRGH!" I dropped to my knees as I felt intense burns all along my body. Gaster laughed in a maniacal fashion. Several flowers were pulverized into tiny crisps.

"I know everything about you, Subject Zero… Your strengths, your weaknesses, everything…" Gaster walked right in front of me. "You may be immune to magic, but you sure aren't immune to the effects of fire on the air. This host has incredibly powerful fire magic!"

"Good for you!" I pushed upwards with as much force as I could, swinging my machete in an upward stroke, only to miss as Gaster teleported away.

"Hmph, do you really think you can hurt me with that puny weapon?" asked Gaster. "In order for you to actually kill me, it will take more than that to hurt me." I stuck my hand into my pocket, and withdrew the small knife that Grillby had given me. The crystal blade flashed in the light, reflecting into Gaster's eyes.

"Ah… you have a transdimensional blade… how pathetic." Gaster raised his hand and summoned a Gaster Blaster. This one opened its mouth, and spewed forth a massive red laser that incinerated the ground into nothing but ash.

"I'm going to kill you in a very painful manner," I told Gaster, holding the transdimensional knife in my left hand and my machete in my right. I wasn't going to be able to use Crosstail while using two weapons, but it was the only thing I could do at the moment.

"I'm sorry, Subject Zero, but I'm afraid that's going to be impossible for you," said Gaster, summoning blaster upon blaster. Each one removing portions of the ground, creating a surface not unlike the moon.

"I've beaten you before, I can do it again!" I said, slashing repeatedly at the undead monster. None of my attacks connected with Gaster, but I was accumulating burns all over my body.

"You're going to die here, Subject Zero, and no one will care," said Gaster, trying to make me feel something. The only thing I felt was an urge to kill the person in front of me. I swung the two blades over and over again, never quite hitting the doctor, and he summoned blaster after blaster. I felt as though I were in an infinite loop, where I did the same thing, over and over until I died.

"I don't care if no one cares if I die, but you need to die," I said, grimacing as another Gaster Blaster grazed my leg. The heat was intense enough to make air burn me, which had me wondering how long I would've survive if I didn't have magic absorbtion. If I were to get hit by a direct laser, I would probably combust due to the heat.

"You are getting tired," commented Gaster, noticing me pant. Most of the room was gone now, just smoking holes.

"I may be tired, but at least… huff… gosh, making inspirational quotes is hard," I said, breathing heavily. "Sheesh, how do they do it?"

"Ha ha ha… you don't stand a chance against me, why don't you just give up now?" Gaster had a smirk plastered all over his face. If I wanted to beat him, I was going to have to be smarter than he was.

"Hmm…"

"Coming up with a brilliant plan, are you?" asked Gaster, laughing. "Nothing can stop me, not even them." He summoned several more blasters and shot them at me.

"Why the heck are you even doing this?" I asked, huffing and swallowing hard. "I can't see any reason why you would even destroy a timeline.:

"That is my reason, and my reason alone," said Gaster in a harsh tone. "You would never understand."

"Why wouldn't I understand?" I asked, trying to stall Gaster as I formulated a plan. "Why?"

"Hmph, when I say you would never understand, I also meant I was telling you," said Gaster. "Stop asking me questions!"

"Come on! Just tell me!" I protested, reaching into my bag slowly.

"Magic doesn't work on me, Subject Zero, don't even try." Gaster watched me through narrowed eyes. "Especially not that pitiful fire magic that that fire monster gave you… He may be a singularity, but he's not powerful at all."

"You know about Grillby?" I stuck my hand all the way into my bag and grabbed three of the shards.

"Being launched across space and time has the benefit of being able to see multiple universes." I took out the fire shards and looked at Gaster.

"Multiple universes, eh? How about a universe that doesn't have you?" I absorbed the fire shards and prepared the final step of my plan.

"A universe without me? That would be…" Gaster's eyes widened. I activated the final step and transferred all the energy to my feet. Fire had the notorious property of being able to expand air at astonishing speed. I forced out the fire from the soles of my feet, accelerating me to speeds not achievable by normal humans.

"NO!" screamed Gaster, only now noticing me. Time seemed to slow as I flew towards Gaster, extending the transdimensional blade towards Gaster's skeletal body. There was a brief pause as the knife pierced Gaster's body.

"Ughh…" There was a slight blur where Gaster stood, and he began fading.

"Nailed it." Gaster blurred in and out of vision.

"If I'm going to leave this timeline… THEN YOU'RE COMING WITH ME!" Gaster roared out, creating a massive fireball around us. I pushed the knife deeper into Gaster even as the fire around me burned brighter and hotter. The air around me was roaring with the sound of fire, burning and spinning. I thought I had gone deaf, until I began to hear voices not Gaster's or mine.

"N-No! He's not my boyfriend, w-where'd you get that idea!?"

"Come on, Frisk! We won't tell anyone! Just tell us!"

"Uh, guys… what is that?" I heard all these voices, as if they were in the burning fireball with me. Gaster looked at me with a slowly dissolving face.

"You won't win so easily next time!" He said, with an insane smile. The heat intensified and I smelled the familiar scent of burning flesh. There was one final roar, and the fireball exploded.

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So, this is the end of the first story arc. Welcome. Now, the second arc will be considerably shorter (I think), than this arc, and it will have less action than this arc. If you want, tell me an Undertale AU, and, if I haven't already planned for it to be added, I might add it in, or something like that. Also, if you have any questions, or if you noticed any plot holes, please notify me so I can fix them. Thanks, and see you whenever I post another chapter, ciao!