"Don't you see Natsu?" Zeref smirked at his brother's repeated attempts to stop his plan. "You no longer have a chance at defeating me, you squandered that chance when you destroyed the demon seed in you and refused to kill me. Now with the power of Fairy Heart, I have limitless magic and can reshape the timeline! Now just give up little brother."
Natsu glared at Zeref while trying to get up off the ground "And let you erase this world? The one with all my family, the one that Igneel died to save? Not a chance you bastard!"
Getting up Natsu began summoning what little ethernano was left in his magical container.
'I've got to make this last shot count. I don't have enough magic to try this again if it fails." Natsu thought as he stood upright and yelled, "Fire Dragon King Mode, Lightning Flame Dragon mode!"
Zeref snorted while crossing his arms "This again Natsu? If it didn't work last time why would you think it will this t…" he stopped abruptly as he saw something different about the form. Was it starting to crackle with lightning?
Smiling at it actually working Natsu said "Like my new form? I call it Lightning Flame Dragon King Mode. Now let's see if you can handle this!" Natsu sucked in a deep breath and cast "Lightning Flame Dragon King's Roar!"
A titanic amount of flames and lightning was blown from Natsu's lungs, almost rivaling the size of Igneels dragon king roar.
'Oh my' Zeref thought.'This might actually hurt.'
Without even time to properly cast his magic Zeref was torn apart by the blast and vaporized. Leaving only a black mist behind.
Natsu mentally cheered as he fell to his knees, not enough air in his lungs to actually say anything. But stopped when to his horror the mist started reforming and taking a human shape.
'Damn it." He thought. 'Guess he really wasn't bullshitting about being all powerful.'
The mist solidified and took form as Zeref once again. Except for this time instead of the smug expression his eyes were now glowing red with rage.
Without wasting a second he outstretched his hand and yelled "Stygian Blast Circle!"
The black death magic traveled from Zeref hands to Natus chest in almost an instant and proceeded to horribly burn Natsu's chest while blasting him back 15 yards away.
Natsu didn't even scream out in pain his body went into full shock. He was barely conscious as Zeref angrily stalked towards him.
"You annoying gods damned brat! What part of limitless magic don't you understand!?" the dark mage snarled "But never mind that, seeing as how you've exhausted your magic supply I can just get on with my pl-" he was cut off once again by an immense rumbling.
'Oh now, what? Is the damned overgrown lizard Acnologia here too?' He thought as he looked around and noticed something odd about the Space Between Time. It was starting to pull apart and crack.
Zeref's eyes widened as his mind started racing 'But why? It doesn't make any sense!' Sure he had stored a lot of pure unstable magic here but he had made sure the dimension was perfectly safe until it was time to use it.
'The only thing that could have made it unstable was if it interacted with other powerful magic. But where did… oh no.'
Both he and his brother, two of the strongest mages in history, had been throwing around city busting attacks for hours on end… in a dimension full of unstable magic.
"Uhh, Zeref are you doing this or what?" Natsu managed to croak out, barely conscious at this point.
Zeref looked at him and knew he should be immensely angry. But it was his own arrogance that had lead this to happen. He could have closed the portal before he followed him but he wanted one last fight with his brother, and now he was paying the price.
Not bothering to answer his brother's question Zeref concentrated. His plan might not have worked, but he would just have to find another way.
His own black magic and the light magic he stole from Mavis started swirling around his body as he focused on the space in front of him. Instead of breaking and ripping as the rest of the dimension was currently doing it started swirling until a vortex opened.
He had know idea where this would take him but he didn't have a choice or time to concentrate seeing as how the world around him was rapidly decaying.
Stepping through the portal he looked back at his barely conscious brother "Goodbye Natsu, maybe you'll meet me in your next life, and perhaps you'll beat me next time. Or maybe you'll just fail again." and with that, he fully stepped through and disappeared.
'Tchh, fucking bastard. I'll get you next time… well if there is a next time.'Natsu thought venomously. His exhaustion fully catching up with him, Natsu's eyes shut right as the dimension finished collapsing.
Unknown Amount Of Time Later
Natsu groaned as something pulled him awake and felt drained. Maybe mixing two of his most volatile modes on low magic reverses hadn't been exactly the best idea.
Opening his eyes all he saw was a starry sky that went infinitely in all directions and smiled. If this was the afterlife than at least he would have a great view.
"Well it would be but you're not technically dead yet my pink haired friend. It seems I was just in time to save your soul from getting ripped apart." An a voice rang from every direction.
"What the hell? Who's there? And it's not pink Jackass!" Natsu said whipping his head around to look.
"My name is Ankhagram, Primordial God of Life and Death." The voice said before it started to appear.
In front of Natsu, a being at least 3 meters tall appeared. He had no distinguishing features, his being entirely covered by a black cloak and hood.
"Hey man not that I'm not grateful for the saving me from the collapsing dimension thingy. But why bother, aren't you against the whole interfering with life and death thing?" Natsu questioned the god remembering how he had cursed his brother.
"Well that's easy Natsu, I have no choice anymore." The god sighed. "Your brother has gone too far. Messing with life and death to bring you back was his first offense and I had let him off really easy. Had he eventually learned his lesson I might have given him a peaceful death. But instead he has not only artificially created demons, he's tried to change the timeline of your world, and now he has gone to another world."
Looking up at the god Natsu asked, "So this has to do with you saving me why?"
"Because your brother broke a major rule by traveling to another universe and messing with its events. As such I've made an exception and I have stopped your soul from going to the afterlife and letting your rebirth in the world he's going to." Ankhseram explained.
Natsu grinned like a madman. Here it was, his chance to even the score with Zeref. But something the god said caught his attention. "Wait why rebirth? You're a god, just send me as I am now."
"Did you not pay attention to anything I said? I was able your save your soul, not your body boy." Ankhseram huffed. "Besides it would have done you no good anyway, the world I'm sending you to is called Remnant. They have no other nano in the atmosphere which means you would be powerless anyway. By being reborn you will have access to a certain power the people there have known as Aura, which is the weaponization of the soul."
"But there is a silver lining to the "This will also put you at an advantage over Zeref as he still retains his old body which will be dependent on ethernano. He will still be able to access the curse, but being without magic will slow whatever his plans down a great deal."
"That sounds good and all, but how am I supposed to deal with him if he still can access your curse!?" Natsu asked starting to get worried hearing he wouldn't have his magic. "Last time I checked it made him so powerful that even his top demons couldn't kill him, hell my regular dragon king mode could barely hurt him! I need access to something else besides some weaponized soul thing if it was enough then you'd just have one of these remnant people do it for you."
"Hmm, seems you figured it out. That's why I will be giving you a gift from another universe to give you some extra, firepower." the god said while outstretching a bony hand and mentally chuckling at his own pun.
Natsu had to close his eyes as a bright flash appeared and then died down. To which he proceeded to raise an eyebrow at what had appeared.
"Really? You're sending to another world without magic and you're giving a goddamn piece of fruit!" Natsu stated slightly mad. He was expecting a sword or some type of power. Not something from the god's backyard garden!
"You idiot this is no ordinary fruit! This is a devil fruit! A Logia devil fruit is known as the Mera Mera No Mi or the Flame-Flame Fruit!" Ankhseram announced while being slightly ticked at the boys disrespectful towards his awesome gift. "This should more than help even the odds for you in the new world. Now take a bite so it's power can transfer to your soul."
Natsu regarded it carefully before he shrugged and took a bite. After all, what did he have to lose?
Swallowing he realized it tasted like fire and ash, which to a normal person would have been disgusting. But hey, it was his favorite. Could use a bit of god slayer flame though.
"So what can I do with this thing?" Natsu questioned.
"That's for you to find out my boy. Now begone and get on with your new life." The god answered and snapped his fingers.
Immediately Natsu's world went dark once again. But not before he heard one final thing from Ankhseram.
"Oh, and Natsu, be wary of this world. You will find that Zeref is not the only evil lurking there."