Kill or be Killed (OLD AND BAD)

Backstory

I stand and look around. I'm alone. Everyone went to the surface. But I can't. Not yet. I came from the surface. I don't remember what it's like there. I was taken for experimentation to the underground. I was taken from all I had ever know. A sweet little baby. Gastor, the one who took me, experimented on me. But he cared for me too. He made me feel fine with this weird, monster-filled world. I lived with him for eight years. I became used to his strange face, two black lines across his eyes. Always smiling. His black robes. And, strangest of all, holes in the middle of his palms. It wasn't grim, or bloody. Just clean holes through his clean, white, hands. At a point about thirteen years ago, he decided to research my soul. Human souls are different from monster souls. Mine isn't different anymore. I have a monster soul now. When I was a little, wee, babe, about two years old, I stumbled upon some of Gastor's other experiments. Small skeletons. They had been created in experiments a few years before I was taken down here. I befriended them, and they played with me like I was one of them. Years later, Gastor was visiting the Core with me, now nine years old, and Sans, one of the skeletons. Papyrus, the other, was at the lab. Too hyperactive for his own good. Definitely shouldn't be visiting the Core. We reached the Center Core after a few hours. The very thing that powers the underground. And then, my life changed forever. I was standing by the wall, talking to Sans. Gastor was leaning over the pit in the Center Core, explaining about the immense power stored in that pit. And then... it must have been a noise, or wind, or maybe he just wasn't paying attention to himself. But Gastor, leaning over the pit, fell. I heard his screams as he plummeted farther and farther down, burning in the energy of the Core. Me and Sans could do nothing but watch as he fell. We decided to leave and get Papyrus, to run to the lab as fast as we could, tell him what happened. Then... we didn't know. When we got back, it was horrible. Opening the door, Papyrus' eyes losing their spark when he realized Gastor wasn't with us. And the look on his face as we told him what had happened. He and Sans left the day after. I stayed in the lab for years, looking through and trying to find anything to help Gastor. But I couldn't go outside alone. It was too dangerous for a human. Only someone with a monster soul could survive out there... a monster soul. When I realized, I hurried to the soul storage room. Glowing balls of energy, floating in glass tubes. There was a soul in every color. Red, orange, yellow, green, light blue, dark blue, purple. And black. A tube with a black soul, giving off an aura of power. I should have gone for that one. It was the most powerful. But I felt compelled toward the yellow soul. I reached out and smashed the glass. The soul vanished. But I knew something had changed within me. I didn't hesitate. I ran out of the lab, leaving my old life behind me. I would find Gastor. And I wouldn't leave the underground until I did.