Spoilers from included and/or represented works abound. Please read this fiction carefully.
"Let's go to Phantom Field." Yu Narukami suggested. "I've made stint there before."
"A calm one calm like once I needed..." Hajun mumbled.
"Enough mumbling. Lets go." Mitra pulled Hajun.
"If you keep messing up, you'll either be hurt by me or get in trouble by others." Magsarion warned Hajun.
The Hegemonies got inside of the DenLiner.
"Your inner power is too strong!" Momotaros, one of Den-O's partners, commented. "I cannot possess any of you!"
"Yeah, the Hegemony Gods is that strong." Yu told Momotaros. "You can't even possess anyone with at least a Taikyoku value of 1."
"Then fine! Ore sanjou!" Momotaros did the iconic pose.
"What Phantom Field?" Ren Fuji asked.
"Mr. Fuji, the Phantom Field created for System No. XX." Yu replied. "More of that when we arrive."
Not long afterwards, the DenLiner arrived at the Phantom Field. (This version was originally created for System No. XX.)
"And look, this looks pretty new to us." Satanael commented. "Who sinned?"
"It's... complicated." Yu then went on to explain everything about it.
"Those chosen individuals from four different worlds being summoned using Keystones?" Ren asked.
"And they had to fight for the Keystones?" Marie asked.
"Precisely. System No. XX was originally an multiversal observation machine, but she ended up becoming sentient and made such tournament." Yu continued.
"So you... has to fight in order to go home?" Reinhard asked.
"We did it a lot." Yu confirmed. "When me and my friends finally left System No. XX for real, like several others, and to our homes, we lost memories of everything about the tournament and its participants."
"I only regained memories of the entire tournament when I suddenly gained some awareness." Yu continued.
"That dimensional awareness..." Hajun figured it out. "That's it! Dimensional awareness allowed people to feel and interact the other worlds!"
"Exactly. I suspect Empress Zero has to do with everything that transpired so far." Yu concluded.
"We gotta find that 'XX' woman!" Magsarion then charged ahead.
"Oh no, wait!" Yu chased Magsarion.
Hajun then stared at the entire atmosphere itself with his three eyes.
Meanwhile...
"We're the Shadows..." Shadow-like humanoid creatures appeared. "The true selves..."
Those Shadow Selves held the initial four Keystones: BlazBlue (blue), Persona 4 Arena (Ultimax) (yellow), Under Night In-birth (purple), and RWBY (red).
"Finally, a zone that complement of my new creation!" A mad scientist appeared out of a Sideways Rift. "Stay here, you Fatui!"
The mad scientist has captured all 11 Fatui Harbinger, including La Signora's coffin.
"Now, with that being said..." The mad scientist unveiled his resulting creation: a Kitsch girl with long bright green hair and a short stature, with soft features and stark white skin in contrast to the pink tattoos on her neck, stomach, and right thigh that reads "PK DICK".
Then, he dressed her up with her (high collar jacket with green accents that go down below her waist, left half-zipped, and a pair of matching sneakers), and brought her to the front of the Shadow Selves. The creature has mechanical prosthetic on much of her right half and has a right arm being a certain flexible bulletproof golden cyberarm.
"Very well..." Shadow Yu, the Shadow Self of Yu Narukami, commented the creature's arrival. "When the time comes... bring on the Ring!"
Meanwhile, the Hegemonies and Yu Narukami walked together to see various other places connected to that particular Phantom Field. Yu Narukami took the opportunity to teach the Hegemonies.
"I'm a Persona user, a human who has the supernatural ability to summon Persona." Yu explained. "After an user obtain their Personas, their physical and mental abilities increase to superhuman levels. Some Persona users can summon multiple Personas, thanks to some Wild Card."
"Not everyone summon their Persona the same way." Yu continued.
"Persona doesn't exist the same way in our world as in your world." Mitra commented.
"Precisely. Because you're all from entirely different worlds than mine." Yu confirmed.
"My friends faced their own Shadowsand came out stronger for it, but I never met mine in person." Yu explained how he grew up as a person and a Persona user. To make up for it, though, I've had my friends to help me mature. It's my companions that I draw strength from in all of my adventures."
After walking a while, they've arrived at June Department Store. However, it is bombarded by the Covenants infected by Sigma Virus. A teddy bear-like creature ran towards Yu.
"Sensei!!!" That creature cried.
"Oh, it's Teddie." Yu noticed the creature. "What's wrong?"
"A walking, talking teddy bear!?" The Hegemonies is surprised.
"You came, Sensei! The Covenants is thrashing Junes!" Teddie reported. "Also, who're these!?"
"Teddie, that teddy bear you're seeing, is also a Persona user." Yu told the Hegemonies.
"Yeah, right!" Teddie agreed. "But who are they!?"
"You mean the Hegemony Gods?" Yu asked.
"What!?" Teddie doesn't even know who the Hegemony Gods are.
"Think of them as both the gods and the multiversal law enforcers." Yu quick speak to Teddie. "No time to explain! Persona!" *summons Izanagi, his Persona*
"We don't have Persona, but we're gods!" Magsarion is ready. "Go!!!"
Everyone then ran and fought the Covenants. With their respective powers in mind, they busyed through a lot of these Covenants. They quickly reached Yu's other friends, the Investigation Team: Yosuke Hanamura (with Persona Jiraiya), Chie Satonaka (with Persona Tomoe), Yukiko Amagi (with Konohana Sakuya), Kanji Tatsumi (with Persona Take-Mikazuchi), Rise Kujikawa (with Persona Himiko) and Naoto Shirogane (with Persona Sukuna-Hikona).
"Persona, motherfuckers!" Teddie summoned his Persona, Kintoki-Douji.
"Leave me alone, you pain in the ass!" Yosuke cut off a Covenant.
"Senpai, you have arrived!" Rise noticed Yu.
slices off Covenants* "Yeah, and I got some help from Hegemony Gods!" Yu then proceeded.
The Investigation Team then outstandingly destroy the Covenants with their Persona and themselves, followed by the Hegemonies finishing all the remaining ones.
"Whew, nice gods you've got!" Chie complimented.
"Hello there, kids!" Mercurius greeted the Investigation Team.
"The Investigation Team? It has me, Yu Narukami." Yu introduced the Investigation Team. "Yosuke Hanamura, Chie Satonaka, Yukiko Amagi, Kanji Tatsumi, Rise Kujikawa, Teddie, and Naoto Shirogane, are the other members."
"We are a group ofPersona usersdedicated to investigating the phenomena of theMidnight Channeland stopping the murder cases inYasoinaba in late 2011."
"Year 2011?" Mercurius questioned the timeline. "My era in my world ended in the 20th century."
"While we dealt with the Cross Tag tournament which involved participants from another worlds, fighting hordes of enemies from another worlds ravaging ours is... well, new to us." Naoto commented.
"The Throne from our world is stolen and hacked by Empress Zero." Ren explained what happened. "Chizuru Urashima managed to optimize the Record of the Throne, the archive, and overclock so that we becomes as powerful as we originally were at our strongest."
"By the way, we're investigating about System No. XX." Yu told the rest of the Investigation Team. "Wanna help those gods?"
"Ok, bro." Yosuke agreed. "We're going to the Hollow Night next."
"Yeah!" Chie and Yukiko both agreed.
"Yes." Naoto agreed.
"All right!" Kanji and Teddie agreed.
"Next stop: The Skyscraper City, Kanzakai!" Rise announced.
"I hope Master Chief don't misunderstand us..." Yosuke commented. "Anyways, let's go!"
The Investigation Team and the Hegemonies went on to Kanzakai, the Skyscraper City. Later, they've arrived in the intersection there.
"Dragonkin from the wrong worlds..." Hyde Kido saw Nowe and Caim as two threats. "What do you expect when someone from another world interfere with me for no reason?"
"But we're trying to help you!" Nowe defended himself and Caim.
"I gotta ask you... Are you a friend of another world you have interacted with?" Linne asked.
"It doesn't matter where we came from." Nowe defended. "We only want to help you save the reality. Just like Agent Jones."
"Yeah? And what if you mess up?" Hyde asked back.
"Guys! We have help!" Yu notified Hyde and Linne.
"Oh, it's you." Hyde noticed Yu.
"These almost dragonic outsiders is messing with us." Linne explain what's happening.
"We don't want to fight against you!" Nowe shouted.
"What's happening!?" The Hegemonies and the Investigation Team approached Hyde and Nowe.
Caim then held a sign which says "We want to help. We want to save the reality. We want our worlds back."
"Hey, why are you arguing with those otherworlders?" Yu asked Hyde.
"They have some... suspicious intentions towards the In-Births." Hyde replied.
"Apparently, they tried to interfere with us In-Births, claiming to wanting to help us." Rinne explained.
Cross-trivia: The False Born,In-Birth, are individuals who control the supernatural powers ofEXS (EXIST, the Manifestation). In-Births are people who are neither alive nor dead - they are people without a(n real) birth.
"Orie told us about them." Hyde noted. "Those Dragonkins first appeared in the Kanzakai Station."
"Here we go again..." Nowe and Caim both facepalmed.
"We're not gonna hurt you this time, dragon idiots." Hyde told the two. "But we won't forget this."
"Watch out!" Marie warned everyone.
Aesir, the God of Chaos from Bayonetta appeared, but infected by Sigma-Virus (hence his skin now being purple with silver and metals for jewelry, as opposed to blue with gold and jewelry.)
"Dude, what the queen beast is this!?" Nowe is shocked.
"Die!" Aesir and threw large energy balls at everyone.
"Persona!" The Investigation Team summoned their respective Persona and got ready for combat.
"Ten gods, eight persona users and two In-Births." Marie counted, including even Yomi who did not speak so far today. "Adding a pact man and a New Breed..."
"We will help you all fight this mutated god." Nowe and Caim stood up for everyone else.
"Then let us make quick work of this." Yu Narukami went ahead.
Everyone went against the infected God of Chaos. So they have used the const abilities and skills to go beat up that. Few minutes later, Caim finishes off Aesir.
"That was quick, partly thank to Persona and those gods." Nowe is surprised.
"You're pact and breed, so you did nice job." Chie complimented.
"Go to Kanzakai Station!" Yu then ran ahead. Everyone followed.
And quickly, once they've arrived there, a man named Akatsuki is fighting a Cube Fiend.
"Akatsuki!" Hyde recognized Akatsuki.
"What? Who?" The Hegemonies has no idea.
Akatsuki then finishes off the Cube Fiend and then approached the party.
"Oh, so it's you and the Investigation Team... and who?"
"We're Heavens from the Throne. The Hegemony Gods, emanating laws across the multiverse." Marie introduced the Hegemonies.
"You're one people who's once involved into the Cross Tag tournament." Yu recognized Akatsuki.
"You look like a pretty super solider." Reinhard commented. "Interesting."
"Akatsuki is a high-class technical officerof the Imperial army, the Imperial Japan's super soldier, and one of the formerGesellschaftmembers. Believed to have died in the Arctic oceans at a critical time after the end of an war, during the transportation of a new military unit from an allied country." Hyde introduced Akatsuki. "Fifty years after the said war, he returns alive and unchanged in appearance. Now wielding superhuman abilities powered by the original prototype Blitz Motor, he resumed his mission."
"I'm Akatsuki. Welcome."
"Yeah, but we should reach the 'Blue with the train." Linne suggested. "After all, if the Phantom Field is still as it is, being crossy and all, we should be able to go to another world thanks to this station."
Without further ado, everyone went into the train that's to reach the 'Blue.
Later on, in the Cathedral (BlazBlue)...
"Team RWBY of the Remnants." Nekron chanted. "Rise."
All the sudden, team RWBY is teleported in front of Nekron.
"Wait what? What happened!?" Ruby Rose is surprised.
Suddenly, team RWBY regained memories of the Cross Tag tournament.
"This place..." Weiss Schnee started recognizing the place.
"We fought... that?" Blake Belladonna remembered.
"You are here to witness the corruption of this universe." Nekron told team RWBY.
"I remember. We used to fight people from other worlds and each other in 2v2 battles." Yang Xiao Long remembered. "But you... you're nobody we know of."
"Oh well... Back to Cross Tag tournament." Ruby commented. "Except not."
"It has been quite a while since we last participated there." Weiss commented. "A lot has happened..."
"I am Nekron, the Lord of the Unliving." Nekron introduced himself. "As recently I'm able to Simon anyone from the omniverse, I can-"
"Unliving!?" Ruby argued with Nekron. "We're basically living a life of Huntsmen as of now."
"Why do you summon us!?" Yang argued with Nekron.
"As I said, you're to witness the corruption of this universe." Nekron replied.
"I feel like it's not fair and game anymore." Weiss sensed something's wrong.
"Is that team RWBY!?" The Ouroboros has arrived.
"Huh? Who you even are!?" Ruby is shocked.
"Noah, Mio, Lanz, Sena, Eunie and Taion. Keves and Agnus, we're Ouroboros!" The Ouroboros introduced themselves
"Help us!" Blake shouted.
"It doesn't matter." Nekron responded. "This universe will be corrupted."
"Shit! Not you again, Nekron!" Lanz recognized Nekron.
"Oh, so you remembered me from Night City?" Nekron recognized the Ouroboros.
"I thought you're dead after the incident with Power Rangers..." Noah is surprised.
"I'm undead. I'm the Lord of the Unliving." Nekron responded.
"Bruh..." Lanz facepalmed.
"Are you going to stop us? No." Taion told Nekron. "We're going to stop you!"
The Ouroboros summoned their respective weapons. Team RWBY also readied their weapons as well, and all fought Nekron.
"Die!" Nekron shouted and started attacking the heroes.
Fighting as an alliance, the heroes quickly traded blows to Nekron, and continued to do so for a while. Then ultimately, the Ouroboros Interlinked and handily overwhelmed Nekron.
"Good thing we're two teams working together." Noah exclaimed.
"Yeah, for the omniverse!" Mio then proceeded.
The Ouroboros then beat up Nekron, while team RWBY escaped.