The Ninth Human: An Undertale Fanfic

Chapter 9: Demonic Storm of the Duat

The whites of my eyes turned black. My pupils became white. On my right eye my iris turned red, my left eye the iris turned turquoise.
Turquoise... something about that is so familiar... I thought.
Now, lets talk for a second. Here's what people don't get about special attacks. You can't just use a special attack. A special attack has a name, and a name is ones identity. You need to give your special attack a presence, give it power. Every being has a special attack. Ones special attack is a magic attack that represents your soul. That's why it's so powerful. You need to speak the name of your special attack to use it.
I lifted my right hand, and spoke the name of my special attack. I didn't think. I just opened my mouth, and my soul spoke through my body.
"DEMONIC STORM OF THE DUAT!"
And suddenly, a burst of red light shot out of my palm into the air. Two massive tornadoes appeared, circling Frisk. I aimed lightning strikes towards Frisk, and it was barely able to dodge due to its gravity being affected by the tornadoes. The judgement hall was ripping apart from the chaos, and to top it all off, I used blue magic as the "rain" of the storm, so Frisk was in an impossible position. It had to move to dodge the lightning and tornadoes, but if it moved the blue magic would harm them. I also noticed I had Karmic Retribution, thanks to Sans helping me in the fight.
Apparently I became the host for Gaster, and he was struggling for control over my body. I decided on something. I decided to join with Gaster. No one would be in control of the body. Me and Gaster merged souls, and we spoke with one voice. Me and Gaster became one being. It helped make the magic stronger.
Eventually, Frisk stopped moving. I was too exhausted to continue the special attack, and my form turned back to normal. My hair turned black. My eyes became normal. My special attack stopped. Frisk was at zero HP, but it refused to die. So I picked up their soul, drained the DT out of it, and the soul shattered. The judgement hall put itself back together. Someone walked through the entrance of the judgement hall.
"Sans? Are you there?" She asked.
I remembered what turquoise was. I knew who the girl was.
The girl was my sister, Sky Koutarou, and she was the soul of TRUST.