I was inspired to write this one-shot by a song called Monster by Imagine Dragons. I hope you like it.

Sonic's P.O.V

It was a dark and foggy night. I happened to be out walking in the woods alone with no fear. Well, maybe a little bit of fear. I recently discovered a deep secret that hid within me and one day it just suddenly happened. I know someone is inside of me but I don't know who he is. All I know is that it looks just like me. I haven't told anyone about my recent discovery because I fear it would scare everyone…especially my friends. Its best if I just isolate myself during the night for that monster is very active at night.

Let me quickly explain what happened a few weeks ago. It happened one night when I was doing my usual late night runs. I was just running wherever my feet took me until all of a sudden I suddenly tripped and fell. I stayed on the floor for a while and started holding my head in pain. I rolled over where I was facing at the dark sky that was sparkling with stars. The pain was awful. I felt like something or someone was trying to get out or control me. The pain lasted for about 5 minutes until it finally stopped. I got back up and shook my head. Suddenly I heard a deep, demonic voice. I looked around my surroundings but I didn't see anyone which I found kind of creepy. I shrugged it off thinking that it was just my imagination and went back home, hoping that sudden behavior would never happen again.

Boy was I wrong…It happened every night for the past 2 weeks and I still didn't know what it was. One night I was in the bathroom and I looked myself in the mirror. I immediately saw myself but it wasn't myself. He had eerie, crimson red eyes and his teeth were sharp and pretty dirty looking. He gave me an evil smirk which kind of gave me goosebumps but I simply rubbed my eyes and found myself again. What on earth was it I wondered…

Third Person P.O.V

Sonic woke up after another restless night. He had the same nightmare again. The nightmare that had been haunting ever since he discovered his deep secret. He always remembered he was running in Green Hill but the sparkling blue ocean was not in sight. Instead, an ocean full of what seemed to be lava or fire burning. He was running but he didn't seem to get anywhere. He felt like he was running away from someone or hiding from someone. Before he knew it, he was face to face with his demonic self. Just when he started to run away, the demonic figure would start chasing him and as soon as he was a few inches close to him, Sonic would wake up panting heavily. He couldn't help but sometimes cry because he had enough of it.

He stood up and dashed to Tails' workshop to talk to him and hopefully he would get some answers. What if he wasn't strong enough to fight what was inside of him? What if the demonic being manages to control him? What will become of him? He couldn't stand the thought of him killing his own friends. He had to do something quick before it's too late.

At Tails' Workshop

"So you think there's an evil being inside of you?" Tails asked.

"Yeah. I know he's inside of me. But I don't understand what he is and who he is…can you do some research?" Sonic asked, his voice full of fear.

"S-Sure thing buddy."

A couple of minutes later Tails came back with a clipboard which Sonic assumed were the results of his research. He felt anxious. But, he was ready to listen to whatever Tails had to say.

A/N: I made this info up okay? It's not like the creepypasta stories or whatever but this is based on how I want it to be. Now let's continue

"Well…?" Sonic asked.

"I found a few facts and legends about what the being might be. It's demonic that's for sure. It's active at night and it loves to hide inside of people every 100 years in hopes to control the body of the person they're in or make the person go insane until they have completely lost it. From what you told me, it seems this being is trying to control your body and claim it as its own." Tails explained.

"Did anyone survive or found a way to get rid of it?" Sonic asked.

"I can't say for sure…I didn't find any info about survivals or how to get rid of it. Most people get killed and are never heard from again."

"What do you call it?" Sonic asked, curiously.

"Whatever the name of the person is that they are hiding in and ends with .exe." Tails replied.

"So… ?"

"I guess so."

"So what am I going to do…?" Sonic asked, upset.

"I don't know…I'm sorry. Maybe I can build something that can get rid of it but it can take a while…I'm not sure what will happen to you by then."

"I can wait…I won't let it get control of me. Just please don't tell anyone else about it alr-" Sonic was cut off by the sound of a door slam. Tails quickly ran to his window and saw a pink figure running away.

"Uh oh…" Tails muttered.

"What?" Sonic asked.

"I think Amy might have heard our conversation…" Tails replied.

Sonic face palmed and ran out trying to catch up to Amy who was not far from where he was. Amy turned back and ran even faster but unfortunately she was no match for Sonic's speed. He was in front of her with his arms crossed.

"Get away from me. You're a monster…" Amy spoke in fear.

"Amy…I'm not a monster…what you heard was nothing." Sonic explained.

"Liar! I heard everything. I can even tell you're worried about it as well."

"Why were you at Tails' workshop?" Sonic asked.

"I had to return something back and I guess I quietly walked in into your conversation…I was going to leave but as soon as I heard Monster within you…I just had to listen. Is it true?" Amy asked, tears forming.

Sonic sighed and slowly nodded.

"What's going to happen to you? Will you still be the same?" Amy asked.

"I don't know…I mean I've been dealing with this for 2 weeks already. I think I can handle a few more weeks until Tails can think of something." Sonic explained.

"Well…I still wouldn't mind being with you if you were to become a monster." Amy smiled. Sonic couldn't help but smile back.

"Thanks Ames. But, I don't want to put your life at risk. I wouldn't know what to do with myself if I killed one of my best friends. You have so much to live for. I think my time might be coming soon…"

"Don't say that. You can't die. I won't let it kill you. You have so much to live for as well and I'm not letting some demon take your life away." Amy responded, crossing her arms.

"No. I said no alright? Look, I appreciate what you're doing but I need to handle this on my own. I don't want .exe to get to you as well. I think he's just looking for vulnerable people to take control over and I guess I was one of them. Anyway…I have to go. I might be gone for a while until Tails comes up with something." Sonic sighed.

"Where are you going?" Amy asked, worriedly.

"Not far. I'll be near. Don't worry okay?"

"Okay…" Amy replied, hugging Sonic. He returned the hug and waved goodbye to Amy before dashing off right in front of her just like he used to do when they were younger. Amy wiped her tears and walked away. A couple hours had passed by and it was already dark. Sonic could feel .exe fighting inside of him to get control over him but he wasn't going to let that happen. Sonic found himself in the woods and began walking with his head down.

Ever since I could remember, everything inside of me just wanted to fit in…oh, oh, oh

"You will never get rid of me. I am with you forever." A demonic voice spoke.

"Get out of my mind! Get away from me!" Sonic yelled.

I was never one for pretenders, everything I tried to be just wouldn't settle in…oh, oh, oh

"It won't be that easy. I have been with you for a long time. I was just waiting for the right time to act."

"You won't get control of me that easily. You've tried for the past 2 weeks and you've failed. You can keep trying all you want." Sonic angrily spat.

If I told what I was, would you turn your back on me? And if I seem dangerous, would you be scared? I get the feeling just because everything I touch isn't dark enough…that this problems lies in me. I'm only a man with a candle to guide me, I'm taking a stand to escape what's inside me… A monster, a monster, I've turned into a monster, a monster, a monster and it keeps getting stronger

"I'm immortal. I can wait until you actually die and take over your body after." spoke.

"At least my soul won't be anywhere near you…" Sonic growled.

Can I clear my conscience? If I'm different from the rest, do I have to run and hide? Oh, oh, oh I never said that I want this…this burden came to me, and its made its home inside oh, oh, oh. If I told you what I was, would you turn your back on me? And if I seemed dangerous, would you be scared? I get the feeling just because everything I touch isn't dark enough that this problem lies in me

"I see your dear friend Amy doesn't mind being taken over. Maybe I'll go for her instead."

"No! Leave her alone! She doesn't deserve your torture. She's too pure for your evilness. Don't underestimate her. She's tougher than you think. I've learned that the hard way…"

I'm only a man with a candle to guide me, I'm taking a stand to escape what's inside me, A monster, a monster, I've turned into a monster, a monster, a monster and it keeps getting stronger.

"This torture is only the beginning for you. I can go extreme if I wanted to but surprisingly you pity me so I'll save it for later."

"Just get out of my body! Get out! I don't want you inside of me!" Sonic yelled, holding his head in frustration.

"Every 100 years I do this. I need a new body to keep me alive. I just choose whoever I think is easy to control. Clearly I made that mistake but I'm not giving up. One day you'll give in. Just you watch."

I'm only a man with a candle to guide me I'm taking a stand to escape what's inside me, A monster, a monster, I've turned into a monster, a monster, a monster and it keeps getting stronger…

"I'm ALWAYS going to be with you. Nothing can get rid of me. You got that?"

Sonic's P.O.V

Those words were repeated in my head over a million times and I feel like I won't be able to keep my promise to Amy and Tails…

A/N: How was it? I like it. I actually might think of making this into a story but that idea might be put on hold because I have 2 other stories I need to finish and if I do manage to finish, I might update this. But, I need some feedback as well. I hope you enjoyed this one-shot! I'll update my other stories soon!