"So....let me get this straight..." Y/n began as she stared at the three exorcist in front of him. Normally this would be a bad idea as he is a devil, but one of them is his childhood friend Jeanne and her two partners, Xenovia quarta and Irina shidou.

He had bumped to the three of them as he was jogging, after reuniting, he had taken them to a quiet place to talk. Jeanne, while slightly upset her friend is now a devil, but she respected his choices.

"Three Excalibur fragments has been stolen by stray exorcists and is being lead by a high class fallen angel. One that was in the great war and is a war monger, and the church sent you three, young exorcists with fragments of your own to retrieve the stolen ones?"

"Correct." Xenovia nodded.

"And you plan to have me and the others stay out of it, as you say you can handle this mess by yourselves?"

"Yup." Jeanne nodded, happy her old friend understood quickly.

"...... YOU IDIOTS!" Y/n snapped as he pulled out a paper fan.

Whack! Whack! Whack!

"Ow!"

"You three are going to face a fallen angel that's been though the great war alone? You might as well hand over your fragments over to them with a silver platter!"

"W-what do you mean?" Irina questioned as she rubbed the area where Y/n smacked her.

"Do you three think your invincible with those fragments? Well think again, your biting off far more then you can chew here."

"And what's that supposed to mean?" Xenovia frowned.

"You think your victory is guaranteed because you have those swords, but that means nothing against someone that went though a war. The experience gap is far too big, you may have three pieces of one of the powerful blades in the world, but you'll lose to someone more experienced then the three of you combined. It's not the weapon that makes a warrior, but the wielder. And in a situation like this, experience means everything"

The three exorcists remain silent, unable deny his words.

"Then what should we do?" Jeanne asked worried.

"Perhaps i can be of assistance?" Overlord said as he took over Y/n's body.

"Who are you?" Jeanne questioned.

"My name is Overlord, the dragon within his sacred gear, the wings of apocalypse."

"I thought your were nothing but a myth!"

"Clearly not, i merely never had a host before now." Overlord explained. "And either way, Y/n will be involved in this."

"What?! Why?"

Overlord summoned Excalibur ruler, shocking the three exorcists.But before they could say anything, Overlord stopped them with an order.

"Silence."

The three shut their mouths at the order, unable to resist the powers of the strongest Excalibur fragment.

"Your question is obvious, why does Y/n, a devil, have Excalibur ruler?" The dragon asked, causing them to nod. " He had a affinity for it as a human, and as for the how he has it, it was granted to him by none other then the lady of the lake herself.

This caused their eyes to widen, they wanted to say something, but Ruler's power is still keeping their mouth shut.

"It's clear in the blueberry's eyes that she wants to shout,"you lie!" correct?". Overlord asked rhetorically. "Tell me, what reason do i have to lie? And with such an obvious one at that?" 

"You think after Excalibur was broken and King Arthur has passed, the fragments would be returned to her, the one who bestowed it to him. But no, she could sense the church's greed to use them to fight against the other to two factions, so she hid the most powerful piece of all. And clearly her instincts was correct, the holy sword project is proof of that."

The three exorcists were shook at the brutal truth they were told, they wanted to deny it with all their might, but as knew Overlord was telling the truth. As he said, what reason to he has to lie?

"Remember, your in Devil territory, you have no right to give orders here. The truce is as razor thin at it is, you would't want to be known as the trio that resparked the great war would you? It'll also only give that war monger what he wants."

Seeing there's something they wanted to say, Overlord decided to hear it. "Speak."

"There's another thing we wanted to talk about, is it true that the witch Asia argento has been reborn as a devil?" Xenovia asked.

Overlord narrowed his eyes . " Choose your words wisely child, as they may be your last." 

This caused her to shut her mouth, not wanting to tempt the dragon of apocalypse to actually go forward with his threat.   

"If you think all devils are automatically evil and all angels are good, your wrong. The fallen angels and the stray exorcists are prove of that. The world isn't black and white, and do you think god hates all devils? If so, why would one of his creations, twilight healing, is able to heal devils as well?."

She opened her mouth to answer, but closed it when she could't find one.

"Despite everything she's been though, Asia is still as kindhearted as she's always been. If you try to hurt her, you'll see first hand why i was and still am the dragon that is feared by all.."

This caused the trio to gulp, knowing it wasn't a threat, but a promise.

He soon let the three to meet up with the others, while he goes to the dimension dragons to discuss what to do. They soon decided the dragons will hunt down the rouge fallen angels while Y/n watches over his teammates.

Y/n then got a text from Ravel that after the meeting with the exorcists, Kiba went awol and Issei, Koneko and Sanji has gone to help with against their kings orders.

This caused Y/n to growl, he was about to spread his wings to find them but something caught his eye. Going to a alleyway, he found a pile of black feathers covered in blood, one he could tell belonged to some fallen angels.  

"What happened here...?"

"I believe i know the culprit."

"Who?"

"I sense the aura of the final dimension dragon, the Starving venom fusion dragon. Be warned, she's the most bloodthirsty of the four."

"Great, like we're not in a bad enough situation as it is..."

"Don't worry, she's still reasonable. However, that doesn't mean you should let your guard down around her." Overlord explained. "I suggest you take priority searching for her, before she encounters and attacks your allies by mistake."

Y/n took flight to search for Starving venom, fortunately she left a trail of blood. Following it, he saw what looks like a mix of a dragon and a carnivorous plant finishing it's meal.

"Starving venom." Overlord called out.

The dragon turned to Y/n's direction before turning into her human form.

"Hey Overlord, never thought you become a sacred gear." Starving venom said as she used a rib as a toothpick. "Who's your host? I smell multiple dragons on him."

"His name is Y/n, but there's no time."Overlord said before explaining the situation.

"More pray to feast on? Goodie~"

"She reminds me of Akeno, but at least she's willing to help." Y/n thought with a sweatdrop.

Y/n looked up to see it's been was late, but suddenly he felt a spike of power coming from the school. Flying quickly to it, he saw it was surrounded by a barrier created by the Sitri to contain the battle. Using the darkness magic he learned from Dust, he opened a big enough hole in the barrier for him and Starving venom to go though.

He saw a massive three headed dog attacking his peerage, so he surrounded himself with fire before crashing into to it's back, causing it roar in pain. The flames then surrounded the mutt and burned it to ash.

"Y/n!" Rias cried in relieve.

"Not Y/n, i'm currently in control." Overlord said." Explain what's going on quickly."

They explained that before he returned, Irina was attacked and had her fragment stolen and is out of the fight before it began. And the one who started it all is a 10 winged fallen angel named Kokabiel has been working with Freed, a psychopathic stray exorcists what's wielding the stolen fragments and Valper, the one behind the holy sword project and is merging the stolen fragments together.

"Kiba..." Overlord growled.

"I apologize for acting on my own, but when i heard of Valper is at Kouh, i couldn't control myself."

Soon the psycho began to mock Kiba while holding up a small crystal, it was the crystalized spirits of those lives was lost in the project. But the mockery soon turned into a cry of pain as Overlord sliced of his hand holding the crystal with Excalibur ruler.

"Silence meatbag." Overlord said as he picked up the dropped crystal and handed it to Kiba. " As much as i want to tear you apart, your life is not mine to take. Besides, i have something else to handle."

He saw the psycho Freed charge at him with the combined Excailbur, he easily blocked the attacks with ease before pushing him back. He then boredly blocked his attacks even when he used the powers of the fragments that made his sword.

"You should quit while your ahead, don't forget, i hold the most powerful fragment of them all, one word is all it takes for your sorry excuse of a blade of break." Overlord deadpanned before looking at Kiba. Small spheres light was floating around him, they are the spirits of his friends that lost their lives to that blasted project, encouraging him to move on.

 "It seems the knight as peaked."

"Peaked? You mean..."

"Indeed, he has achieve his balance breaker, a sacred gears ultimate state. It's next level you could say."

"Balance breaker, Sword of Betrayer!" Kiba declared, summoning  a sword that's has both holy and demonic energies running though it.

Before Valper could rant about the impossibility of such a sword, Starving Venom tears off his head to silence him.

The surprises don't end here, Xenovia revealed she wield Durandal, another holy sword that rivals Excalibur. Together, they both managed to shatter the combined Excalibur and knock Freed out. Kokabiel, in hopes in crushing their spirits revealed that the biblical god was fallen during the great war, shocking almost everyone and even causing Asia to faint.

 But before he could continue his monologue, Overlord snapped his fingers and caused a small fire explosion near the fallen's feet, causing him to fly in the air to dodge.

"Do you really think i'd be rattled by old news?" The dragon asked sarcastic. "I was still unsealed at the time of the great war and i had to burn a flock of you crows during that time remember? A flock you led if i recalled, i spared you so you'll nurse your wounded pride for the rest of your pathetic life. It was a mistake it seems, one i plan to fix."

 "You made the mistake of causing the seven fragments to gather in one location, now i can kill two birds in one stone."

Overlord raised Excalibur ruler into the air and called on the power Vivian given Y/n when she handed him the blade. "Reunite"

Ruler sent out a golden pulse across the battlefield, causing, destruction, blessing and the pieces of the combined Excailbur to glow and float towards Overlord. The three blades became light practicals that was absorbed by Ruler, which soon erupted into a pillar of light. When it died down, it revealed in his hands was he true Excailbur, completed at last.

I know many people doesn't like to compare the Excalibur of Fate and DXD, which is why i'm going to crack up it's power to match it's fate version

"That's the true Excalibur?" Rias asked, even though she was quite the distance away, she felt quite weak due to it's holy aura.

"Incredible..." Xenovia could only let out, in awe of the sight of Excalibur being complete once more.

Suddenly a dark aura manifested from Excalibur before it formed a black sword that looks like Excalibur.

"So this blade still exist? Excalibur morgan..."Overlord said before grabbing with his left hand before giving back control to Y/n.

"Oh? Why did he gave you control again? Is the dragon of apocalypse that afraid of me?"  Kokabiel mocked.

"Afraid of you? Oh please, your not worth his time." Y/n scoffed as the boosted gear appeared on his left arm, the gem glowed brightly.

"Welsh Dragon, balance breaker!" Ddraig called out as red armor formed around Y/n's body.

"Y/n unlocked his balance breaker? Somehow i'm not surprised.." Kiba said, getting nods from his peerage. They know how hard Y/n can train, and with Overlord and Ddraig teaching him, it was just a matter of time before he obtained it.

Y/n suddenly appeared behind Kokabiel before swinging Excalibur at him, the fallen leader managed to block the strike, but it sent the crow crashing to the ground. Not wasting any time, Y/n surrounded himself with flames before crashing on him like a flaming meteor, creating a large crater.  

Y/n then flew back a few feet before he created a large sphere of fire and throwing it at the fallen, the sphere then broke into multiple smaller ones, causing the fallen to block the rain of attacks with his wings. 

"Blazing dragon shot!"

Y/n fired dragon shot infused with fire at Kokabiel. the attack hit it's mark, sending him though a building. Flying after him, Y/n saw Kokabiel was weakened but alive and his wings are burned off.

"M-my wings.." Kokabiel could only groan out.

"For an angel, fallen or not, the number of wing signifies their power, rank and status, for one to lose some, or in your case, all of them, it's really a blow to your pride isn't it." Y/n mocked as he walked up to Kokabiel. "Now to finish this." He formed another dragon shot.

Suddenly the barrier surrounded shattered as something flew near them.

"Hold up, red dragon, my mission is to bring him back alive." The figured said he flew closer.

Y/n knew well who this is, this was is rival thanks to being the red dragon emperor, the white dragon. 

"So your allied with the fallen angels, white dragon?"

"Hello white one, i see you decided to show yourself." Ddraig called out from the gem in Y/n's left hand.

"Hello red one, i see you have quite the interesting host." A voice could be heard from the white dragons wings.

"Indeed, though after a talk with Overlord, maybe it's time we put an end of our centuries of fighting." 

"Hm, it does sound fun, it's nice to talk to you casually, i look forward to our next meeting Ddraig." 

"As do i Albion."

"I'm glad to see your strong my rival, lets have a fight when we next meet." The white dragon said before he took off with an unconscious Kokabiel and Freed.

Y/n deactivated his balance break as Rias rushed to him for a hug, Kiba walked up to her to apologize and to repledge his loyalty to her, though she forgives him, she still gave him a spanking for going rouge. 

Timeskip

The next day, the ORC got an unexpected visitor in the form of Xenovia, who became Rias's second knight after she was exiled from the church for knowing the truth of the biblical god's death, with no real purpose, she all but begged Rias to reincarnate her . As for Irina and Jeanne, they both returned to the church, the former feeling betrayed and the latter was still with them as she didn't say anything about god's death.

Starving Venom had joined her sisters as Y/n's familiar, the four were happy to be together again after being apart for years.

As they celebrated a new member joining their peerage, Y/n could only wonder what the future holds.

Done and done, next time Y/n and the others will relax at the pool and Y/n might meet a someone unexpected. What do i mean? Read to find out. Also, should i add other elements from fgo? Tell me in the comments bellow.