A/N: This was requested by... @AlphaWolf1107!! (This is my laptop so, I'm not sure whether it tagged or not...) Thanks for this request! I may have had fun writing it :3 (Like I do with all my requests from my fantastic readers ^w^) I was also curious on how this would work but I like how it turned out! Now onto the story!!

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(Mario's POV)

Unlike usual, we were all together with everyone in the guildhall, just chilling. Ritchie and Brandon were talking with each other on their little step thing? David was talking to Lucas, who was trying to read a book, and Bjorn was talking with Inmo about their Viking training. Tapio was playing around with some plants he found. I had my eyes closed as I was having an internal conversation with my brothers.

(Mario, Colin, Bryan, Mitch)

'So, how're your days going?'

'Good! We're all just chilling in the guildhall. Even Michael's in here instead of his office!'

'Yeah, it's weird. Even he's having a drink with us.'

'Well, that's weird, but at least he's finally out from doing paperwork. Bryan, how's your day?'

'Fine so far. Lo-Pho's just talking with Bri while Jakey and Kay are making lunch!'

'Wait, they can cook things other than cookies?!'

'Yeah. Even I didn't believe it till I tried their lasagna. Oh boy, I would DIE to eat that again!'

'Now you're making me hungry!!'

'Hehe, oops? Anyways, Mario! How's your day going?'

'Eh, the usual. Just everyone talking and-' I stopped myself when I felt a weird presence like the presence was familiar yet it wasn't from anyone from the guild.

'Mario? You good?'

'Yeah, you suddenly stopped. Did something happen?'

'Uhh, yeah I'm... good? I'm gonna leave for a bit because I felt a weird presence just then...'

'Uh Ok? What do you mean weird 'presence'?'

'It was a familiar presence but it doesn't belong to anyone in the guilds.'

'Well, that's weird... Anyways, stay safe. We don't want a repeat from a few weeks ago!'

'He's right. You let us know if something happens alright? Remember, we're only a call away.'

'Yeah! Just call us if something happens! We may still feel if somethings off but still! Stay safe, big bro!'

'Thanks, guys, we'll talk later.' I feel them each leave my head after saying their goodbyes.

I open my eyes to see my guild members and leaders still carrying on with their conversations. I look around to see where that weird presence is coming from and I think Ritchie and Brandon noticed.

"Mario, is something up?" Ritchie asked and now everyone was looking at me, a little concerned.

"There's a weird presence somewhere and I felt it just now..." Both of my guild leaders eyes widened a little when I said that.

"So, we weren't the only ones feeling it?" Brandon asked, sounding a bit worried.

I nodded my head. "Yeah, I felt it too. But this presence felt... familiar to me for some reason." I saw that Ritchie was about to say something but I was suddenly blasted up against a wall, which really hurt. Everyone got into defensive positions as David and Tapio ran up to me.

"Mario! Are you alright?!" Tapio yelled as he checked me for any injuries and David helped me sit up.

"Y-Yeah... T-that just hurt al-" I was interrupted by a big cloud of smoke engulfing the room. When it disappeared, I didn't want to believe who was in the middle of the room.

"Hello again, Mario..." Dean said in a dark and evil voice.

Everyone one around him tried to attack him but he dodged all the attacks. Suddenly, he manages to freeze everyone, so all of them except me, Tapio and David can't move. Then he walks towards me slowly even as David stands in front and Tapio wraps his arms around me protectively.

"Excuse me, but I need to get to that traitor so, move." He sounded a little agitated but David didn't budge. Dean then blasted David across the room, like what happened to me.

"D-David!" I yelled and tried to get up but it just made me groan in pain so I stayed down. Now Tapio was standing in front of me like David was before.

"Move, little kitty, If you know what's good for you!" Dean raised Tapio in the air and launched him out the open door.

"T-Tapio!" I yelled again but gripped my side as I groan in pain again. Dean smiled creepily at the damage he's done and then nods his head before he starts walking towards me again.

"Dean! Stop! We will have you arrested if you do not stop!" Ritchie yelled but Dean used his powers to strengthen the spell he has on him, making Ritchie groan in pain and he squeezed his eyes shut tightly.

"Brother!" Brandon yelled, looking over at his brother in worry and concern.

"Now Mario..." He knelt down to me as I backed away from him against the wall, ignoring all the pain and my body shaking. As I backed up, he moved forward until I couldn't move anymore. He forcefully grabbed my neck so that I was looking at him, straight in the face.

"First you decided to fail a very simple mission, then you blame me for something that happened to your sister, and then you run away from the guild? Thinking that I'll just let you rat us out? I don't think this will go unpunished."

He doesn't let go of my neck as he reaches into his pocket and pulls out a weird crystal-like thing that was a dark green colour. I heard a gasp coming from both of my twin leaders as they both start yelling at Dean to stop and start threatening him. He ignores the yells and proceeds to forcefully shove the crystal into my body.

I screamed very loudly as painful magic started flowing through my body, tears were rolling down my eyes from the pain. Dean had a satisfied look on his face and lets go of my neck, allowing me to grip my head and stomach as I curl against the floor. I can hear my guildmates yelling at me and Dean, concern and anger clear in everyone's voices.

"Welp, my job here is done! Mario, enjoy~" He laughs maniacally as he disappears into thin air, only leaving particles behind. Once he's gone, everyone was able to move and they all came straight to me, to which I was shaking, crying and whimpering in pain from this new magic. Kit ran over to where Tapio was thrown and David was slowly getting up.

"Mario! What hurts?!" Brandon knelt in front of me and placed a hand on my shoulder, a panicked and worried aura surrounded everyone.

"E-E-Everything!" I yelled as I grip my head with both my hands when a sudden wave of pain hits me. I then felt someone slowly pick me up and then we're all on our way out the door, presumably going to the infirmary. Everything hurts and I felt exhausted so, I passed out in said person's arms.

A few hours later...

I honestly felt like Bjorn ran me over when I woke up. I woke up in the infirmary, and I tried to sit up but I groaned in pain instead so, I just lie back down on the bed closing my eyes in the process. Then, I heard multiple footsteps and look over to see my guild leaders and members all walk into the room.

"Mario, you're awake!" Kit yells as she runs up to me and hugs me, making me wince in pain. She backs up after apologising.

"W-What h-happened?" I croaked out.

"Dean showed up and attacked us, mainly you, Tapio and David," Ritchie explains, my eyes widened as I remember what happened. Tapio and David walk into the room with bandages on both of them. I then look down to see a bandage around my arms and around my chest. Then, I remember the crystal.

"W-What was t-that c-crystal?" I mumbled but Brandon and Ritchie heard me.

"That was a devil slayer lacrima..." Brandon sighed. I tilted my head as I didn't know what that was. Ritchie saw this and continued with explaining.

"A devil slayer lacrima is a crystal that can give a person magic powers. You were all trained or born with your powers whereas my brother and I had our's forcefully placed into our bodies. Mine was a lightning devil slayer lacrima while Brandon's was a wind devil slayer lacrima..."

This shocked most of us except David, so I guess he already knew this.

"S-So..." I trailed off, looking at the twins, hoping that what I was thinking wasn't true. Unfortunately for me, I was right, since they both looked at me with sympathetic looks on their faces as they nod their heads.

"Indeed. You had a devil slayer lacrima inserted into your body. That makes you a cavern devil dragon slayer." 

I looked at the ground, thinking about this newly processed information and how I'm going to tell my brothers about it. Then, a sudden jolt of pain goes through my body and I scream in pain again. The others are trying to talk to me but I couldn't understand any of them. Instead, my hearing went fuzzy and my vision went blurry as I continued to scream and thrash around in the bed.

Then, there was a white light...

When the white light as faded, everyone has backed away from me, looking at me with a mix of scared, concerned, worried, angered and intrigued faces.

"W-Why did you all back away?" I asked. Honestly, my back feels heavier and my head hurts.

"Mario... This isn't you..." David whispered. I didn't know why he was whispering, did they not hear my question?

"Hehe, I know it isn't him. Allow me to introduce myself. My name is Terrai and I am the demon of the Cavern Devil lacrima! I'm going to say, I wish Dean didn't pick such a weak individual for me to be stuck with. Oh well, at least I'll be able to take over him easily." A weird voice came out of my body, sending shivers down my spine.

Most people growled at 'Terrai' as he just laughed.

"Give us back Mario!" Ritchie yelled, anger clear.

"Well, you're no fun! Fine, you can have your puny dragon slayer back. Or should I say, devil dragon slayer? Just remember, I'm always here~" I feel myself get control back as the weight on my back is lifted and the pain on my head is disappearing. I open my eyes and everyone is still looking at me as if to make sure it's me and not Terrai.

"Oof. N-Now I see how it feels to have a demon in you..." I place a hand on my head as a headache starts to form.

"Yeah, it's not fun. I guess now we have a devil dragon slayer in the guild. We're gonna have to teach you how to use your new powers, which come with the lacrima." Brandon shakes his head.

"I think I'm going to head back to bed. Today's been rough, and I still have a headache." I say tiredly as I yawn after speaking. The twins nod to accept my request, David walks over and picks me up bridal style, even though I can walk myself. "David, you know I can walk myself, right?"

He shakes his head. "Nope, not letting you. You still have some broken ribs and plus, as you said, you have a headache. You're also exhausted so, just sleep and I'll get you home." He smiles down on me, even as my face blushes a little. I just accept the fact that he won't put me down and snuggle into his chest, falling asleep instantly.

'MARIO!!'  I heard all of my brothers yell in my head.

'What?'

'What happened?! Why did you not responded?!'

'Yeah! We've been trying to talk to you for the past few hours when we felt your pain!'

'What happened exactly?'

'Look. I'm exhausted and it's been a rough day. Dean attacked our guild, technically just me, David and Tapio, and I only just got out of the infirmary just now.'

'EXCUSE ME?!'  I internally sighed as I have to explain.

'Pretty much. Dean threw me and David against the wall, he froze everyone in place so they couldn't stop him, Tapio was thrown through the open door. Once he reached me, he inserted a lacrima in my body and I passed out not long after. Then I woke up here and long story short; I'm now a Cavern Devil Dragon Slayer and have a demon named Terrai in my body who is insane.'

I could feel all of their anger and concern coming from them and I sighed again. 

'Listen, I'm going to sleep because as I said before, I'm exhausted. I'll explain when our next meeting comes so, just hold off on the questions and someone may come with me for protection and watching to make sure my demon doesn't take over.'

I can hear them protesting but I leave my headspace and see that I'm in my bed just as David was about to leave. I grabbed David's arm, pulled him into the bed and snuggled into his side, instantly falling asleep.

I feel him freeze, then his arms wrapped around me protectively and I smiled as I fall asleep, peacefully for once.

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Jeez, that was a lot. Anyways, sorry it took so long. It's now 3:00 pm and I started writing at about 10:30 am-ish? Also, the next oneshot is SNO!! Poketail Origins will be uploaded VERY shortly~.

Enjoy!

-HangryWolf

P.S: Should I draw Demon Mario, a.k.a Terrai?