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freeze your heart out, let me shatter it

Summary:

Silver reaches out to Gray after the Grand Magic Games, and grants him demon slayer powers, as well as information on E.N.D. and Tartaros. Determined to avenge his family, and prevent any more atrocities, Gray decides to go undercover in the demon guild and kill E.N.D. in his own home.

But E.N.D. is nothing like he expected, and for some strange reason, the demon of all demons forms an attachment to Gray, and it's only a matter of time before he's grappling with feelings he never expected. Natsu isn't the monster that was described to him.

But he knows he can't give up this mission, even if he has fallen for the very demon he came here to kill.

Notes:

I saw a prompt for this FOREVER ago by sunflowerandsnowflake on tumblr, and it has been consuming my every thought ever since. Me and RevlisCharm talked about it a lot and I wanted to get it written in fic form (with a slightly happier ending than we originally talked about lmao)

Anyways, here, have this

Chapter 1: Prologue

Chapter Text

Erza stared at the ragged cross, at the vicious icicles clinging to it, the snow swirling around it. Two names had been carved into the old wood: Gray and Mika. Gray’s name had been crossed out, but honestly… she thought that might have made it sadder. 

There were no bodies beneath the cross. Most of the bodies from Deliora’s attack had been decimated. Torn and crushed and burned beyond recognition. Or at least, that was what Gray had told her, one of the rare few times he’d opened up about what happened in Isvan. 

And she assumed… that was the reason Gray’s father had never questioned Gray’s death, despite not having a body. 

Until the Grand Magic Games, of course. 

As gentle as possible, Erza stepped over and took Gray’s hand, giving it a soft squeeze. “We should find shelter soon. It’s going to get dark.” They’d been standing here for hours now, and while she certainly didn’t want to rush him, they couldn’t stay here forever, in the ruins of Isvan, surrounded by empty graves. 

Her friend took a deep breath, and reached up to brush away the tears that had frozen on his cheeks. “How could that happen to him?” he whispered, and Erza had to strain to hear him over the howling wind. 

“It wasn’t fair,” she said, brushing her thumb across his hand. “No, it was wrong. Beyond fucking wrong. But he can rest now.” 

Gray grit his teeth. “Those fucking demons.”  

“They’ll get what’s coming to them,” she promised. “Even if we have to hunt them down our damn selves.” She may have never met Silver, his reunion with Gray followed by his death had only lasted a few hours, but she knew he hadn’t deserved the years and years of torture he’d endured at the hands of the Tartaros demons. 

“E.N.D.,” Gray hissed. “Dad, he—he told me he was the one behind everything. That if he died, the others would be easy to pick off.” 

“Cut the head off the snake,” Erza agreed with a curt nod. 

“I want to do it.” He squeezed Erza’s hand, so tightly it began to ache. “I want to kill him my damn self. I’m not going to let that fucking demon hurt anyone else like he did my family. Dad said he was cocky, proud.” 

“Gray—” 

“I could do it.” He ripped his hand out of Erza’s, calling on the strange new magic that he received from Silver just before he died. Demon slayer magic. “I could get close to him, and I could do it.” 

“No!” Erza gasped, as soon as she realized what Gray was insinuating. “Gray, think about what you’re saying, we can’t infiltrate—” 

“You can’t.” He pulled away from her. “But I can. Dad said demon slayer magic can be unstable, I can act like it took me over! And then I’ll join their fucking guild, and get him to trust me, and then I can end him!”  

“You are not going into a place like that alone!” Erza exclaimed. “I don’t care what you say, how confident you are, what you think you’re capable of, I’m not letting my best fucking friend put himself in danger like that! One slip up and you’ll end up in the same hell that your father did!” 

“Or I could kill E.N.D. and make sure that this never happens to another person ever again!” He turned his gaze back to the pathetic grave. “Demons ruined my life, Erza. I’m not letting them do the same to anyone else ever again. I’m doing this, I’ve been putting it together ever since Dad told me about Tartaros. And I’m going to infiltrate them, with or without your help.” 

“Gray… please. Please, just calm down, think it through. I will help you hunt them down and kill them all, but not like this,” she said, shaking her head. “Not like this.” 

He turned away, stomping through the snow. “I’m doing it, Erza. You’re not going to tell me no.” 

“Gray!” She rushed after him, already opening her mouth to argue more, but she stopped herself. She knew how stubborn he could be, how much he was hurting right now. Not only had he just found out the horrors that his father had gone through, but Gray had killed him with his own two hands, just to put him to rest, to end his suffering. Her friend had every right to want revenge, and she knew Gray well enough to know that he was going to do this. He’d made up his mind, there was no changing it. Which meant… 

Which meant the best way to protect him and keep him safe, was to offer her support and do what she could to help him. 

“What do you need me to do, Gray?” 


“Why are you doing this, Gray!?” Erza wailed, raising her sword to block a dagger made of ice. “We trusted you, we loved you!” 

Gray grit his teeth, not deigning to answer. He just threw attack after attack at his best friend, narrowly dodging any swords or lances or knives that were flung back at him. He could admit, he’d been worried about Erza’s acting skills. They’d failed them in the past, but… she was doing really well. 

So well, that it was making uncomfortable feelings well up inside Gray’s chest. 

Black markings crawled across his skin, eating him up, leaving even him feeling cold, like he was freezing from the inside out. Or maybe he was just trying to not let Erza’s words get to him. 

It’s just an act, just an act, just an act. 

“Don’t do this, Gray!” Erza begged, rushing forward to press her sword against his chest, right against his Fairy Tail mark, the signal they’d agreed on to finish this. 

The entire street had been destroyed. The cobblestone was torn up, buildings collapsed, spikes of ice towering out of the earth, with numerous swords and knives sticking out of them. They’d demolished an entire portion of Magnolia in this staged fight, and while Gray felt guilty over it, they’d known they needed to do something drastic if anyone was to believe he’d really snapped. 

A month of buildup had led to this, ever since they’d formulated their plan in the ruins of Isvan. Every now and then, Gray let his markings show up, pretending he hadn’t meant to do that and that he had issues controlling them. He’d snapped at people more often, gotten more… violent during spars or guildhall fights, and it had all accumulated to this. 

Going on a mission with Erza, taking things too far, and when she attempted to scold him for it, he’d attacked her. 

It’s just a spar, just a spar. He couldn’t let this get to him. He was going to have to go through far worse, do far worse, if he was going to last even a few days undercover in a place like Tartaros. Especially if he was going to stand out enough that E.N.D. took notice of him, let him get close enough that Gray could strike. 

He needed to be viscous.  

He took Erza’s sword, forcing his ice to crawl over the blade. I’m sorry, he mouthed, not daring to actually say it, in case one of the horrified onlookers heard him. 

The heartbreak didn’t leave Erza’s eyes, but she whispered, “Good luck.” 

The blade shattered, breaking into a million pieces, the metal unable to handle the cold and the frost and the ice. While Erza was “distracted” with her broken blade, Gray slashed up with a knife of his own, giving her a shallow cut across the cheek. 

Erza stumbled back, her hand flying to her face to try and hold the cut shut, blood trickling from between her fingers. 

And Gray ran. 


Gray glanced over his shoulder, calling on his magic and letting it build on the tips of his fingers. Someone had been following him for the last mile, at least. He could feel their eyes on him, a deep, menacing presence, that he’d only felt a rare few times. 

Demons.

After five weeks of wandering the wilds, searching out the Tartaros guild, maybe they’d finally come to him. 

He tightened his hold on his demon slayer magic, determined not to let the markings slip now, of all times. It’d been hard at first, keeping the markings on at all times, but he knew he’d be forced to keep them there his entire time in Tartaros, so he needed to get used to it. Fight through the itchiness, the soreness, as well as the less than savory urges his demon slayer magic could cause. 

He took a deep breath, and spun on his heel. “I know you’re there.” 

“Well, I would certainly hope so.” A woman dropped down out of a tree, offering him a wolfish smile. “If not, I think I’d just kill you on the spot.” 

Gray bared his teeth. “Who the fuck are you?” Not human, that was for sure. Never mind the physical abnormalities, she had that intense, smothering presence of a demon, dark and deep and menacing. 

She waved him off. “Oh, that’s not important at the moment. I’m more interested in you.” She crept closer, her unnatural smile stretching even wider. “Silver’s son… Dear old Silver, who went off and got himself killed.” 

Gray clenched his fists, but forced himself not to react any further than that. 

“You’re on the run, aren’t you?” she asked, digging out a piece of paper from her bag, skimming it over. “Yes… Gray Fullbuster, former Fairy Tail mage, wanted for questioning.” 

Wanted for questioning? Well, Erza must have carried through pretty well on her part of the plan. He’d been relying on her to really build up how he hadn’t been acting right, how something was wrong, and if he was wanted for questioning she must have done a damn good job. She was the only one who knew the truth of what he was doing, and he could only hope she didn't crack and reveal it to the wrong people. 

But all he did was shrug. “I wouldn’t know. I haven’t talked to anyone in weeks.” 

The demon hummed. “And why is that?” 

“I’ve got better things to do than interact with fucking humans,” he growled. 

“Oh… wanting to follow in dad’s footsteps? You’ve been out here looking for us, haven’t you?” she asked. 

“Yes. Dad told me about your guild before he died. I want to join.” 

“And why should I believe that you’re genuine? You’ve been in a light guild before now. You’re not even a demon.” She reached out, running cool fingers over his markings. “Despite what you’re trying to prove with these markings.” 

“My dad was loyal to you, I’m loyal to my dad, and he gave me this magic, this demonic magic. I wasn’t meant to be with light guilds. They turned on me the second this magic took me over. My best friend turned on me.” This was his first test, convincing this demon that he could be trusted. 

“Well… I can admit you are interesting Gray,” she said. “And even if you prove to be nothing but a filthy, lying rat, you’ll make a nice plaything for my dear Seilah. So come with me.” She turned, motioning for him to follow. “My name is Kyoka, and I will take you to Tartaros.”