Seal of Rapidity
[A/N - Hey everyone, thanks to a comment I realized that I based the names for the Devil clans wrong. Cassius' Clan, Lazarus will be changed to Naberius which unlike Lazarus is a name actually in the Ars Goetia (Which is what the actual 72 pillar names are based off of) So, thanks, Rivo, for pointing it out!]
CLANG
Their blades clashed as sparks flew off, It was clear who won the exchange but Cassius' heart still shook a bit as he noticed while, Excalibur's Holy Might only slightly suppressed his sword, Os-Gladii, his own sword did absolutely nothing.
His sword might as well been a regular steel blade as it's demonic aura didn't even effect the Holy Aura Excalibur itself gave off one bit.
After the brief clash they have a better understanding of each other's physical strength.
Arios panics a bit inwardly as cold sweat drips down his back, 'Devils are much more stronger than Humans, he barely put in any strength!'
Arios thought back to his training and remembered Vivian always told him technique can overcome the difference of physical strength.
Cassius sneers as Arios' panic is visible on his face then,
"Oh?" Cassius says unconsciously as he noticed Arios' face change into one of absolute focus.
Arios decided to fight.
Arios positioned himself in a high guard before his feet dug into the ground as he launched himself from the ball of his foot towards Cassius. He grips Excalibur with both hands on the handle and slashed downwards from the top of his shoulder.
The blade slashes towards Cassius' chest but Cassius wasn't willing to wait and get hit. Cassius quickly responds by trapping the blade in his sword's hilt as Excalibur was still slashing towards his chest. He uses the opportunity to stab towards Arios' chest with Excalibur still trapped in Os-Gladii's boney hilt.
Arios' instincts scream at him and without hesitation jumps to the side, narrowly dodging the blade while simultaneously freeing Excalibur from Os-Gladii's hilt.
They both back away while panting, they soon pick their stances once again, as Cassius takes an aggressive but flexible Roof Guard with both hands raised above his head but not to the extent of a high guard, and his blade pointed out from his back.
Arios takes a defensive Plow Guard pointing outwards towards Cassius with both hands on the handle, causing Cassius to have to act.
Cassius does an overhead slash that Arios quickly parries which causes Cassius' strike to fly the opposite direction, Cassius quickly reels his strength to perform another overhead slash but from the opposite direction. Sparks fly as Arios was able to once again parry.
Cassius was starting to get angry, while he knew he had to get serious and couldn't mess around in this fight, his inborn arrogance and pride took over, 'How dare this lowborn beast stand against me!' In his anger he stopped thinking for his next move and only began to act reflexively, throwing overhead slash over overhead slash, one after another.
Arios quickly noted the growing repetitive nature of Cassius' strikes and decided to soon use it as an opportunity.
For the next overhead slash, Arios suddenly and quickly partied high causing Cassius to flinch at the unexpected parry and lose a bit of his footing.
Not letting up, Arios quickly thrust forward launching his blade at Cassius' face. Cassius in his panic barely managed to react, quickly jumping back and slapping Arios' blade. His innate reaction did more harm than good, bathing his hand in Holy Aura which he let out a loud grunt of pain as the skin of his hand began to char.
Arios still didn't let up regardless, changing the direction of his blade and attempting a circular cut towards Cassius' neck.
Cassius already reeled in his shock and quickly parried Arios' blow, then hastily responding with a slash. Arios dodges to the side taking the opportunity he saw as Cassius' hand was extended, he thrust Excalibur's point towards Cassius' hand managing to stab into it.
"ARHHHHGGGG!!!"
Cassius roared in pain, his hand had been pierced and in turn, bathed in Excalibur's Holy Aura, the aura was akin to acid as it destroyed all the vessels and skin on his hand before spreading to the muscle and bone, reducing his hand to ashes.
Soon the pain subsided as Cassius looked towards his hand, only to find nothing but his blade resting on the ground.
Soon he roared once again, but this time not in pain, but rage,
"You FILTHY HUMAN SCUM!!"
Picking up his blade with his already charred remaining hand, he pumped it and his arm full of Demonic Energy, reinforcing it and helping subside the pain from his charred palm.
He executed one powerful slash after another, his speed quickly picking up as his aggression only further enhanced his demonically enforced physical capabilities.
Arios can barely keep up as one slash after another rapidly picks up speed, his parries also become gradually slower as each of Cassius' overbearing strikes only serve to further numb his arms.
Panic begins to set in as Cassius picks up pace even further, soon Arios begins to become littered in cuts and minor slashes, the demonic aura didn't make it any better as it would burrow into his skin, burning him from within, while the pain caused him to slow down even further, as it soon cycled repeatedly.
Cassius' lips began to extend outwards, curled in a cruel smile.
Arios was in panic, he didn't have time to activate his sacred gears as any loss of focus would kill him. He grit his teeth in anger, not at his opponent but, himself. He was an idiot, he should have trained himself more, if only he was stronger he could stop the numbing in his arms, if only he was faster he could keep up.
'I don't want to die.'
He hasn't even made a name for himself yet, hasn't even had a chance to really live, he would lose Excalibur, he would fail those he wanted to protect, he wouldn't keep his promise with Vivian, he would die a virgin again and most of all he would have to see that shitty god again.
'Fuck no!'
'I'm not gonna die here!'
As if responding to his will to survive, Excalibur glowed and Arios heard a clink in his ears as if a gear had been shifted.
Soon words popped into his head as if they were always there but he knew it was from the blade he held in his hands, he soon yelled them out and Excalibur responded in turn,
"Second Seal of Rapidity, Disengage!"[1]
FOOOSH
A golden aura exploded outwards from Excalibur before covering him, the demonic aura seeped his my skin was quickly vanquished before he soon felt the aura's effects. His muscles gained a new understanding of fluidity as their inner flexible was greatly enhanced.
Cassius flinched from my sudden remark alongside Excalibur's release but quickly reeled it back in and continued his onslaught.
But this time, the tables were turned and Arios responded in kind.
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[1] I'm making my own seals for Excalibur so, each seal releases a certain ability. Excalibur will be a very story involved object that Arios will gradually need to unseal more of. It doesn't have the seals from Fate but still has seals unlike DxD while the abilities are based off DxD.
CREATORS' THOUGHTS 
RISE10
RISE10 Hey everyone, I hope you enjoyed this chapter, it was my first time writing a sword fight so I hope it was good enough.
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