Diamond Is Unbreakable

-BANG!!

-BANG!!

-BANG!!

Crashing through several castle-like structures and destroying a couple of houses in the process, the people of the Diamond Kingdom were forced to flee as Grim and Lucifero's battle tore up their kingdom.

-SLAASH!!

Swinging his sword and unleashing a slash that was capable of vanishing by cutting through space and appearing right in front of Lucifero like it had teleported, panic covered the devil's face as he manoeuvred his body to evade the slash. Barely managing to evade the attack in time, the slash continued cutting through space travelling an unimaginabled distance and slicing through dozens of buildingsand unexpecting humans.

"NOOO!!!"

*BANG!!*

Running out of the castle followed by a lot of Mage Warriors, Mars and the human Fana only managed to make it a few steps before they were quickly forced to their knees.

'Arrgh!!'

'What the hell!'

'My body feels like its being crushed!'

Even Ladros, the attribute-less mage whose only real ability was absorbtion and emission was unable to bear the intense levels of mana.

'This, is this the end of the Diamond Kingdom?!'

"HARGHHHHH!!"

To focused on their own battle, both Grim and Lucifero flexed their powers without holding anything back. For the citizens with low mana or unlucky enough to be near the two while they were teleporting around, their bodies exploded on the spot unable to withstand the pressure the two were emmiting.

Making a popping sound, blood rain fill the sky as the colour drained from the faces of Mars and the others. But without the strength to even stand there was nothing that they could do. They couldn't even see who or what was attacking their kingdom. There presence here made no difference.

As for Grim and Lucifero, the Devil and Elf didn't concern themselves with the lives of the dead humans. They were nothing more than ants that just happened to be in the wrong place at the wrong time.

*BANG!!*

Colliding again, the shockwaves from their blows rippled through the air bringing about endless devestation and turning the area they were fighting in into a lifeless wasteland.

'This boy! He's a beast in human skin!'

*SWOOSH!!*

*BANG!!*

*BANG!!*

*BANG!!*

Teleporting again and grabbing onto his face, Lucifero treated Grim's body like a battering ram as the two smashed through several more buildings killing many more innocents in the process.

[A/n: Think of the train scene from Invincible.]

"HAHAHAHAHAHA!!"

Despite being covered in the bloody remains of several humans, gleeful laughter erupted out of Grim's mouth as he threw the Devil king onto a running couple crushing them underneath.

"THIS IS NOT A JOKE!! STOP ENJOYING THIS!" He screamed his rage destroying everything around him.

Grinning, Grim used the blood on his face to draw a bloody smile.

!!!

Watching such a disturbing scene, Lucifero felt his heart skip a beat as he also felt what Nahamah and Lilith felt during their final moments.

'This boy is dangerous.'

'I should have stayed in the underworld.'

Nothing he did was working. Punching and kicking was useless, [Gravity Magic] it was immediately devoured, even his overwhelming mana that he was so proud of only made Grim act more like a crackfiend seeing that sweet sweet white powder dangling in front of him.

If only he had manifested with his full power.

On the other hand, Grim was thorougly enjoying himself. The 0th form had far exceeded his expectations.

Not only was he cutting and devouring space like it was nothing, he was even capable of replicating other magics/spells without trouble. Even Yami's [Dark Cloaked Dimension Slash] wasn't off the table. The slash he did earlier that teleported held similar principles. Asta also did something similar with his [Demon Slasher: Infinite Slash Equinox]. Thus Grim dubbed his attack as the [0th Form: Vanishing Slash] and [Vanishing Slash Equinox] for when it has to travel a further distance.

Outside of replicating magic, both his body and strength had reached a level that he found shocking. While his previous physical strength was nothing to scoff at, compared to what he had now it wasn't worth talking about. Not to mention the perks of his invulnerability.

But more than anything, the [0th Form] proved that all his hard work wasn't for nothing. That all the training he put himself through was worth it. That what he did wasn't in vain. Compared to this, what did the death toll of a few hundred or something humans matter?

Seeing that this fight wasn't going the way he wanted, Lucifero came to a decision.

'I can't stay in this world!'

In order to feel at ease, he only had one option left.

Return to the underworld!

If he could fuse with his other half and achieve his full power, would he have any reason to fear Grim? Even if he did, how long could Grim live for? If he just kept his head down and stayed in the underworld surely he could outlast him? Right?

With this thought in mind, he immediately ran.

"Hey!" Grim called racing after him. "WHERE DO YOU THINK YOU'RE GOING! WE'RE NOT DONE HERE!"

Soaring through the air and trying his best to put some distance between him and Grim. The two travelled several miles in a matter of minutes.

"STAY AWAY FROM ME YOU GODDAMN MONSTER! HAVEN'T YOU HAD ENOUGH YET! DO YOU EVEN KNOW HOW MANY PEOPLE YOU'VE KILLED?! YOU KILLED MORE THAN ME, THE DEVIL KING!!"

"SO WHAT?! SHIT HAPPENS, STOP LIVING IN THE PAST AND FIGHT ME!"

'What the hell is wrong with this guy?!'

"I SWEAR TO GOD LUCIFERO! IF YOU DON'T STOP RUNNING RIGHT NOW I'M GOING TO MAKE THIS HURT SO MUCH MORE THAN I INITIALLY PLANNED!"

"EITHER WAY I GET HURT!"

"I'M A DEMON SLAYER NOT A MIRACLE WORKER!"

Ignoring him, Lucifero continued flying away as fast as he could. Before they knew it, the two finally reached the Spade Kingdom.

'I made it!'

Unable to teleport due to his close proximity to Grim, Lucifero's only option was to reach the area he had manifested from and hope that he could use his [Gravity Magic] to tear a hole between dimensions using the unstable space and re-enter the underworld.