Cerberus paled as he tried to find a way to calm sweet Seele as she oozed her authority as the Herrscher of death while her scythe drew his blood. 

"Now, Rex-Onii-chan," Seele whispered as her eyes slowly bled red. 

"Seele, are you here?" A holographic image of a beautiful young woman appeared causing Cerberus to pale in fear and immediately disappear in an amber flash. 

"Kiana-Onee-Sama!" Seele said with a smile. "I found him!" 

"You did?!" Kiana shouted as she looked around. "Rex! Your ass is mine when I get there!" 

Cerberus, the former archon of geo and current Herrscher of the cosmos hid behind his newest adoptive mother's back. 

"Is she your girlfriend?" Guizhong asked teasingly. 

"Best friend really... she must still be pissed." 

"I know where you are! You better show up or Elmo gets it!" Kiana roared out loud.

"Bullshit! Rin has Elmo! I put it on my will!" Cerberus shouted only to yelp when a sub-space lance almost speared his head when he stood up. 

"Calm down, Kiana," Elysia said as she gently pushed Kiana out of the hologram. 

"Ooh! Hi Auntie Ely!" Reese shouted causing Elysia to raise her brow. "Uncle Rex is hiding from Auntie Kiana! I already finished my homework!" 

"Okay, behave there," Elysia said with a gentle smile, 

"I will!" Reese said. 

-----

Timeskip

-----

Cerberus, a.k.a Rex Crozzo, hummed as he sat inside a heavily fortified multiple-layered revolving barrier as he ignored how Seele pouted at him while Veliona lied on her stomach as she ate some snacks with him. 

"Well, since we have just finished the viewings, do you have any questions?" Reena asked as she looked at the audience. 

"I have! What's a Herrscher?" Paimon asked as she floated beside Lumine. 

"Well, Paimon. A Herrscher is a human that has merged with Houkai energy and has given into the will of the Houkai to destroy the current era of human civilization," Reena said as Cerberus and Veliona ignored the conversation as Cerberus closed his book. 

"Think of an Archon amped up to eleven," Cerberus said as he looked at the people from Teyvat. "Each one of us has a special ability such as Uncle Welt's Mimicry or Seele's authority." 

"Wait, aren't you a Herrcher too?! Are you going to destroy Human civilization?!" Paimon asked as she looked at him. "No! Stay away! I won't let you hurt Lumine!"

"Well, yes. I am a Herrscher, the Herrscher of the cosmos," Cerberus said with a smile. "And no, I won't destroy Earth's human civilization because my Herrscher self was way easier to contain than my Herrscher powers. Honestly, just sneezing is enough to create a dust fall," 

"What about those bitches?" Seele asked while he wisely ignored the question. 

"Uhm, who was that skeleton on the throne?" Asta asked her unofficial Fiancee, who smiled brightly. Reappearing beside her, Cerberus smiled as he wrapped an arm around her as Seele sharpened her scythe while her Belobog counterpart ordered if her other self was dating Cerberus. 

"To know about him, my dear Asta, is a blessing," Cerberus said as he adhered to the Bro code. Feeling how close he was to her, Asta blushed bright red.

"I vote for Miss Asta, little one," Guizhong said, handing some Mora to Reese. 

"I vote for Madam Bronya," Gepard said as he handed some shields to the child.

"I vote for Lady Asta," Arlan said with a smile as he and Peppy handed Reese some money. 

"I vote for Ganyu," Zhongli said with a smile, causing the Adepti to turn red. 

"I vote for Yan Fei," Madame Pings said, smirking at Guizhong 

The end result ended in Reese taking note of all the money she had made. 

"Reena! Hit it!" Sighing at the antics and how much Rizz her father had when he was focused on things, the princess of Finality turned the theater on. 

"It is the 41st Millennium. For more than a hundred centuries The Emperor has sat immobile on the Golden Throne of Earth. He is the Master of Mankind by the will of the gods, and master of a million worlds by the might of his inexhaustible armies. He is a rotting carcass writhing invisibly with power from the Dark Age of Technology. He is the Carrion Lord of the Imperium for whom a thousand souls are sacrificed every day, so that he may never truly die.

Yet even in his deathless state, the Emperor continues his eternal vigilance. Mighty battlefleets cross the daemon-infested miasma of the Warp, the only route between distant stars, their way lit by the Astronomican, the psychic manifestation of the Emperor's will. Vast armies give battle in his name on uncounted worlds. Greatest amongst his soldiers are the Adeptus Astartes, the Space Marines, bio-engineered super-warriors. Their comrades in arms are legion: the Imperial Guard and countless planetary defence forces, the ever-vigilant Inquisition and the tech-priests of the Adeptus Mechanicus to name only a few. But for all their multitudes, they are barely enough to hold off the ever-present threat from aliens, heretics, mutants - and worse.

To be a man in such times is to be one amongst untold billions. It is to live in the cruelest and most bloody regime imaginable. These are the tales of those times. Forget the power of technology and science, for so much has been forgotten, never to be re-learned. Forget the promise of progress and understanding, for in the grim dark future there is only war. There is no peace amongst the stars, only an eternity of carnage and slaughter, and the laughter of thirsting gods."

All could only look in horror as the brutality of the 41st millennium was shown on screen as Cerberus glowed in pride. 

"You went there all the time?" Dainsleif asked. 

"Yup! It was fun! I conquered more than ten thousand worlds for the imperium and Charles and I get to play Paradox-Billiards-Vostroyan-Roulette-Fourth-Dimensional-Hypercube-Chess-Strip Poker with Charles," Cerberus said. 

"In the grim darkness of the imperium, throughout countless centuries, the Amber Monarch, the emperor's black hand appeared and reappeared, cleansing, capturing, and reforming countless worlds in the image of what the god-emperor has envisioned. He leads the forces of the Imperium of Mankind in its darkest hours, turning the tides. Even the dogmatic Black templars, follow his command as he once lead their founder, Sigismund, the black templar." 

"Under his lead, technology, and knowledge once forgotten returned and flourished. The forces he lead became legends just as he lead his lamenters, a century of amber-visored Custodes, through countless conflicts. He is the Amber lord who blazes the path of progress forward, eradicating all those that oppose or seek to harm mankind into nothingness, destroying countless worlds with a blink of an eye. 

...

"Okay! Enough! I will be showing some parts of Cerberus' life," Reena said, unable to bear her father going onto another tirade of his time in the 40K verse. No offense to Uncle Charles but her father would end up seducing more girls if he does. 

"Wait! No!" 

"Run that by me again?" A younger Cerberus, around 16, said as he raised his goggles, revealing his dirty face, and lowered his soldering iron as he looked at his older brother. "You mean to tell me, you forgot big sis Ely's birthday gift?" 

"Yes..." Reinhardt said, looking at his feet, 

"The same big sis Ely that stood by your side no matter what, the same person that helped you raise us, the same person that made sure we won't be as much violent as possible, and more. And you forgot her birthday gift?" Cerberus sighed as he rubbed his nose. "How are we still alive?" 

"Hey! Elysia was the one in charge of you two! Don't diss her work!" Reinhardt said with a pout. "But the truth is that I don't know what kind of gift I should give her," 

"A baby, preferably yours, or a wedding ring," Cerberus said bluntly as he set his work, a metallic cube, on the table.

"Come on, Rex! Stop joking! Besides, Ely deserves someone better." Reinhardt said while Cerberus sighed. 

"Okay, I know one gift she would love but I need to make some calls," Rex said as he looked at his phone. "Better tell it to them personally,"

"You two look the same," Lumine said, wondering who Elysia was

. 

Rex, now dressed in a white button-up. a pair of ripped jeans and rubber shoes, fixed his wristwatch as he entered an underground facility. Nodding at the guards, the young man went inside a room. 

"Hey, Ana! I need a favor!" Rex shouted as the light opened to reveal Kiana Kaslana with her hair down, walking down the air.

"The sustainer!?!" Lumine shouted, as fear coursed through her veins and grabbed the closest person to her, which was Cerberus who already lowered the barrier. 

"Hey, Rex!" Ana said with a grin as she landed on the ground. "So, what's the occasion?" Kiana asked with a smile. 

"A date," Hearing this, Kiana blushed and held her cheeks. 

"Aw, man. You know Mei is already the number one in my heart," Kiana said with a grin, swaying from side to side while Rex rolled his eyes.  "But, if it is you..."

"Not with you," The entire theater felt the sudden drop in temperature as Kiana's eyes turned to gold for a split second, making Lumine hold onto Cerberus tighter and the young man gently squeezed her hand, remembering how he felt when he watched Morax's memories. "I need your help to prepare a date between Rein and Big Sis Ely," 

Just as the temperature dropped, the temperature returned to normal as Kiana grinned brightly and hugged him tightly. 

"I'll ask Mei and Bratnya to help us!" Kiana said as she snapped her fingers, revealing it to be his room in the Crozzo family bunker. Kiana grinned as she turned around and jumped towards the bed and lay on her stomach as she opened one of his drawers that contained her clothes. 

"I didn't know you and Auntie Kiana were that close," Reese said as she effortlessly dragged a sack behind her while Cerberus held onto Lumine, unsure of what to do to help calm her down. 

"Kiana and I were childhood friends," Cerberus said as Lumine looked at him. "We shared a lot of things together and she often finds a way to drag me to her adventures if I am not busy," 

"My, my~" Herta said with a grin. "You really are a deviant, already having a girlfriend and you still proposed to my dear lead researcher," 

The news made Guizhong cheer in joy while Asta blushed. Seele turned to him mechanically and smiled sweetly. 

"Well, Kiana is not my girlfriend but my ex-girlfriend and I broke up a long time before I arrived in the space station," Cerberus said, shocking most of the audience. "And no, I won't tell you who-," 

An image of Wendy Aelous playing the harp appeared on screen as she dressed in the same Archon clothes as Barbatos alongside a long-sleeved archon-robed younger version of Cerberus appeared on the screen. The former archon had a smile on his face as his amber-streaked dark hair tied into a high warrior's wolf tail and amber eyes glowed fondly while he created several Adeptus sigils. The screen then showed an image of Wendy kissing him on the edge of his lips as he tinkered with the Memory of dust, causing the Geo Archon's progress to be halted as he froze in place. Despite having no blush, the amber highlights in his hair glowed brightly. The screen then showed a series of images showing Rex drinking a cup of coffee only for Wendy to jump on him, pin him on the bed, and an offscreen photo of Wendy throwing their Archon robes off their forms.

Zhongli and Venti looked at each other before shivering in horror at the sight that just happened. 

"Eeek! My fanfic came true!" A random person from Liyue squealed. 

"Reena!" Cerberus screamed as his face had a cloud of red dust on his cheeks. 

"Well, well. It seems like my dear researcher's chance got higher," Herta said with a teasing smile. "Curator, can we perhaps have some clothes similar to those on screen?" 

"After the viewing Miss Herta," Reena said with a gentle smile. Seele smirked, having read with Bronya about Cerberus' fetishes on his hidden stash, commandeered by Kiana. Veliona stayed away from her counterpart until. 

A portal was slashed open inside the theater as Mei Raiden, a look-alike of the Raiden twins, stepped inside. 

"Seele," Mei greeted with a smile, and her eyes hardened as she looked at Cerberus only for her to reappear in a lightning flash in front of the former archon with her Katana soaring to his neck. 

Cerberus did nothing as time and space distorted themselves around him and caused him and Lumine to reappear on the stage as he formed an amber Zweihander and blocked another attack from Mei. 

"Well, I got enough time to kill," Cerberus said cockily as he looked at Mei, effortlessly matching her blade lock. "Wanna dance, origin?"

"I'll make you pay," Mei said coldly as she pressed her katana. "Cosmos," Her purple eyes glowed as the Cosmos and Origin jumped away from each other. 

"I'll bet 20,000 Mora on Mei," Makoto said with a cheerful grin to her niece who nodded as the audience looked at Cerberus and wondered if all women that knows him will try to kill him. 

----

Got bored so here is Rex's power-scaling (may be higher on lower depending on the use of Adeptus Arts.))

Rex, Crozzo knight (pre-archon and herrscher): Multi-city block level
Rex, Anemo Vision:  City level
Rex, Geo Archon (pre-bleeding): Mountain level
Rex, Geo Archon/Anemo Vision (Post-bleeding): Continent level
Rex, Archon of the Earth: Moon level
Rex, Joyful Lord of the earth/Archon form + Adeptus arts: Planet Level
Rex, Maddened Joyous Lord of the earth/ Archon + Adeptus arts + Cascade: Large Planetary level
Rex, Herrscher of the Stars: Solar system level
Rex, Herrscher of the Cosmos: Multiverse level
Rex, Pathstrider of Harmony (Pre-entombment in the amber throne): Hyperverse level
Rex, Ruler of the Amber throne: Outerversal level, similar to Finality Kiana.
Cerberus, trailblazer and Herrscher of the cosmos, (post amber thron-entombment, vision loss, gnosis loss,): Multiverse level
Cerberus, the trailblazer of Akavili: (residual geo archon powers and Adeptus arts only) Star-level