@nanaxthexfox requested this.

Situation : There is the headcanon of Nightmare being sick from the beginning, since his magic is to overwhelming ( it isn't mine, but I don't know who owns it ) , and Dream tries to heal him by giving him a golden apple. That obviously didn't work, and Nightmare becomes corrupted. ( A Glitchs Nightmare uses this headcanon )

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Nightmares P.O.V.

I was terrible sick since the beginning, the doctors said it was because of my magic, but they didn't really try to help me. They would probably kill me, if Dream wouldn't die, too. We have a balance, if one dies, the other will die too. So they'll try to keep me alive, but nothing more. But I'll die soon, anyways. I can feel myself getting weaker each minute. And Dream keeps on beliving I will live, no matter how sick I am. Well, he's made of positive emotions after all. I'm not sure if I should be thankfull for his optimism, I'm probably even a little bit jealous if I think about it. But he seems so determined to keep me, he offered me one of his apples so many times, but I can't take one. I would be punished, no matter the intentions. I tried to tell him that so many times, but he just won't listen.

Dreams P.O.V.

I know my brother will survive, I won't let him die ! But he keeps on denying my help, my apple... Why can't he just accept my help ?! I needed to do something, so I decided to give him a golden apple without his knowledge, it was for the best, ... right ?

Everything is ready, I made an apple-pie with one of my apples, my brother is going to be okay again ! I called him to his favourite cave, he likes to hide from the angry villagers in here. I tried to keep them away from him, but they won't listen. They hate him more than anything, but blame him for their hate at the same time. I just can't understand that, why would it be his fault ?

" Hey Dream, everything alright ? Are you worrying about something ? " , Nightmare said, while entering the cave. The moon was shining, showing the weakened body of the negative guardian, way weaker than just a few years ago. I felt happy, knowing my brother would be better soon. But...something kept on nagging on my mind. What if Nightmare had been right all the time ? What if someone would punish him ? I brushed it off, my plan will work.

Nightmares P.O.V.

Dream called me to my favourite spot, an isolated cave where I was safe from further damage. I didn't think anything of it, he was my brother after all. I got there, not without a few coughing fits, but who cares, just to find Dream seemingly thinking. His emotions were a mess, I hope it isn't about me, I never intended to hurt him in any way. He seemed to be nervous, too.
" Here, I brought you a piece of apple-pie somebody made for me. You should try it, it tastes really good. " , he said.
" But it was made for you. Why would I deserve a piece of it ? " , I replied, it was his cake after all.
" Brother. You deserve everything. Now eat up. " , shrugging,I took the pie.
It smelled odd, but nobody ever gave me pie before, so I can't judge properly. I took the first bite, then the second, and Dream was staring at me the whole time. I finished the pie quickly, but Dream won't stop staring at me, and it's starting to creep me out. There was hope in his gaze, but also a hidden fear. Suddenly, I broke into another coughing fit, but this time, I started to throw up at the same time. I throwed up a weird, dark, liquid, but it didn't stay on the ground. It started to climb up my bones, quickly consuming their white. My sight started to get blurry, but I couldn't pass out now.
" D-Dream ? What did you do ? "
" I-I didn't mean to...Oh no...Nightmare are you alright? "
Thankfully, I could see properly again, but my back started to ache now. As if something that was caged for an eternity decided to brake out. I couldn't bare the pain, so I clinged to Dream in an attempt to make it stop. There was a sound of something shattering, and finally, the pain stopped. Strangely enough, I could feel some sort of extra arms, but they seemed to be more flexible.
" Drea- " ,I wanted to ask him what happened, but stopped right after opening my mouth. That wasn't my voice! It sounded darker, threatening even.
Dreams P.O.V.
What did I do ?! A strange liquid covered the fragile frame of my brother, and there were four dripping tentacles growing from  his back. His voice sounded different, too. A single blue eye, cold as ice, was looking at me desperately. I shouldn't have ignored Nightmares words. But he seemed so broken now...I achieved the opposite of my goal. Trying to stay positive, I pulled him into a hug.
" Don't worry...It's all gonna be okay... " , I didn't know who I was reassuring right now, probably myself.
He seemed to be surprised, but he hugged back either way. Apparently, he was controlling the tentacles, too, since they wrapped around me as well. We sat there for hour's, I didn't want to let go, and Nightmare was trying not to freak out about the new...circumstances. He calmed down after a while, but he didn't pull away.
" You know that I can't go back like this, right ? I don't want to snap and accidently kill the entire village. "
We both knew that he was right, even if I didn't want to believe it.
" Wherever you go, I'll follow. I want to stay by your side forever. " , I made my decision, and nobody could stop me from doing what I want.
" But Dream- "
" No buts. "