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The Greater Cosmos

Summary:

Waking up in a world far from his own, displaced in space-time, shrouded with the tumultuous history of Godlike beings, how can one possibly return home? With futuristic tech, but the slow, dominant rise of destructive forces, who could come and hold the pillars of the world on his shoulders?

Ben Tennyson, two years after saving the entire universe, after an experiment gone wrong, now finds himself in a foreign land overseen by cosmic deities called “Aeons.” In a world filled with advanced science, paths, philosophical powers, and enigmatic forces, Ben must face all these challenges to thrive in this strange new environment.

Along the way, he meets new friends and clashes with various foes. Even after maturing, old habits never waver as trouble constantly finds itself on the hero's path. Follow Ben as he is tangled in the fates and destiny of new worlds, once again stepping up in his role as a hero!

Notes:

PS: This is my first ever attempt at writing fanfiction. The story is essentially based mostly of Honkai Star Rail's plotlines, but if Ben 10 was in it. Chapters are expected to be released once every week.

Chapter 1: Stranded

Chapter Text

Travelling through universes is usually quite a vivid and mesmerizing experience, except when it causes fractures in the fabric of space-time. Today, that is the exact situation Ben Tennyson finds himself in. Even now that he’s much older and more mature, his habit of attracting trouble has never faded an ounce. 

He looked around the strange building he found himself in. He then looked upwards. There, he spotted a massive blue-lit sign stenciled to the wall that flickered weakly. It read:

HERTA SPACE STATION — SUPPLY ZONE

“A space station?” He asked himself before peering out of one of the many large windows in the area. He squinted through the cracked window where he could gaze at the glimmering planet below. 

Beyond that, he could vividly see the vastness of space, the stelliferous quiet void filled with various celestial bodies floating peacefully and ethereally in the distance. He looked surprised at the sight, yet at the same time, not so much.

“So I’m in space, huh? …There’s actually a rather nice view up here.” He commented silently under his breath.

For a Supply Zone, instead of the usual sterile hum that you’d always hear and find somewhat annoying, it sounded as though you were inside that of a whale’s stomach; silent, pitch-black, humming faintly with static energy. The lights were out, and so was the backup. The emergency generators were fried, and everything that could flicker with a spark of electricity was dead.

After a few brief moments of silence, alarms then started blaring loudly all around the strange building he finds himself in, producing a dissonant cacophony that made it hard to focus. At the same time, heavy marching footsteps echoed through the dark halls. 

As people dressed in armed and reinforced black suits started coming into view, Ben slipped behind the nearest massive storage crate to evade their view, his boots silent against the cold floor. Even without light, his instincts threaded the shadows like old friends. Being nineteen didn’t magically erase the decade of bizarre emergencies wired into his reflexes. 

He peeked over the crate, watching them from his hiding space intently as they looked around for clues. The building was currently undergoing a massive power outage, and the light of flashlights illuminated the dark, cold halls. The guards carried guns powered with a strange foreign energy that Ben wasn't familiar with from his home world.

Wait… Those things don't seem to be powered by manna… Wait, am I in an alternate dimension of some kind?!?

Worrying thoughts about his situation started swirling in Ben's mind. But those thoughts were quickly cut off when he saw that the guards were led by a dark-skinned, grey-haired boy, who looked barely over his teen years, which surprised Ben. It was not often that you’d see a young boy leading a pack of grown men. 

 “Stay alert. Spread out. Maintain formation. The power grid doesn’t collapse on its own; something caused this.” The boy spoke in urgent authority.

His fingers brushed the watch-like device on his wrist slightly. The instinct to go, hero started flickering in his mind like an instinct. Go stealth, defensive, something that could at least talk him out of this misunderstanding before it escalates further.

Ben tried to remain hidden, though ultimately, he was spotted by one of the guards, who immediately alerted the boy to the presence he had detected.

“Brother Arlan! Movement behind that storage stack!” He said in a startled manner, as the rest of the squad raised their weapons in caution.

Soon, the other guards too detected the same movement. Their weapons raised instantly, the energy powering them humming louder. Ben sighed. Intentionally loud enough for them to hear. He slowly stepped out with both hands raised.

“Hey. Uhm… Before anyone shoots anything, let’s skip the whole aggressive interrogation thing, yeah? I kinda just got… thrown here. I didn’t exactly walk in through the front door. More like… fell in from another dimension?” He pleaded in a calm and steady tone, not wanting to cause any more unnecessary drama.

Silence. A long silence. Arlan exhaled through his nose as though he was fighting off a headache. “Dimensional displacement is not a ‘funny story.’ Do you take us for fools?” Arlan retorted with skepticism.

“Look, I get it. Sounds crazy. But I promise you I’m not here to cause issues. Something went wrong, big portal, even bigger explosion, and now I’m… here.” Ben hoped that he would somehow buy his excuse. Thankfully, while Arlan didn’t exactly believe him, he could see that Ben was unarmed: shooting at unarmed civilians isn’t exactly something an honorable guard would do.

Arlan held up a hand, signaling the guards to hold. He stepped forward, assessing him with sharp, disciplined scrutiny. “Alright then, if that’s the case, identify yourself. This is a restricted area reserved for personnel of Herta Space Station only.” He said firmly.

Ben weighed honesty against the possibility of sounding insane. He chose honesty anyway, after all, insanity was sort of baked into his life already. He offered them an awkward wave of his hand.

“Name’s Ben. I’m… not from around here. Long story, again, weird portal, accidental crash-through-a-window situation. And before you ask, no, I’m not here to sabotage anything.”

The guards tensed; Arlan’s posture didn’t soften, but his eyes sharpened with critical curiosity. Weapons twitched upward again. Hearing the sound, Ben winced slightly at the sound of their rifles charging.

“If you’re not hostile, then step away from the crate. Slowly. Any sudden movement and they will fire.”

But before he could utter another word, the sounds of heels clacking on the floor could be heard rushing in their direction. They both turned to where the sound was coming from, and out came from the shadows a girl, a beautiful woman in her very early twenties, with pink hair and white streaks. With a soft voice, she exclaimed,

“Arlan! Status?” She said in a hurry, catching her breath. It was clear that she likely sprinted down multiple floors to reach wherever they were currently as quickly as possible.

“Miss Asta, I was just about to apprehend the intruder. This person just randomly appeared out of nowhere as soon as the blackout occurred. Found him hiding. Claims unintentional arrival.” Arlan turns and points to Ben.

She took in the scene before her: guards with raised weapons, Arlan tense, and a stranger covered in dust, exhaling with a practiced sigh. After a moment, Asta exhaled, the tension in her shoulders loosening. She spoke in a practical tone of voice.

“Let’s de-escalate, please. Lower your weapons. If he hasn’t attacked yet in this lighting, he’s probably not here to harm anyone.”

Arlan hesitated slightly but nodded after a moment of consideration. Listening to her command, the guards lowered their weapons slightly.

Asta’s gaze then lands on Ben, who was still dusting off the dirt on his green and black jacket. She observes the young man standing before her; he looked ordinary, and his outfit and clothing barely matched most standards they have. He gave her a small, sheepish nod while brushing off dust from his green-and-black jacket. His expression radiated the peculiar mix of worry and world-weariness belonging to someone who had seen too many bizarre things. Then, as if struck by a freight train of realization, her brows rose as she spoke softly with just as much curiosity.

“You don’t look like you belong to any affiliated world. Clothing standard is… unconventional. And you said something about a portal?”

Ben brushed off more dust from his jacket. “Not even remotely close. I got yanked through a portal. Not my first interdimensional mishap, but definitely one of the weirder ones!” He replied honestly.

She listened carefully as he explained. Ben’s voice was steady despite the utter madness of the situation. The details aligned too perfectly with what she knew happened just minutes earlier in the Special Purpose Lab, which is what caused the blackout in the first place.

With dawning realization, she muttered softly under her breath with a slightly troubled expression forming on her face. “A portal… during a power failure… That lines up suspiciously well with a… certain experiment.”

Arlan shot her a look, already piecing the implications together. Asta nodded back to him, decisively telling him to activate the holographic transmission device. “I need to notify Lady Herta immediately.”

Ben’s eyes perked as he overheard her words and let out a quiet remark, “Looks like I was the unlucky one standing at the other end?”

She turned to Ben, speaking politely. “Please remain with us. There’s a lot we need to clarify.” Ben simply nodded, offering her a half-smile of cooperation.

Asta exhaled, her mind spinning through theories and protocols. A situation such as this was unprecedented. She has partaken in countless risky experiments before, but none such as the one presented before her. A variable from a completely different dimension migrated to theirs as a result. She quickly pulls out a disk-like communication device and begins speaking to the person on the other end.

“No restraints. No hostility. He’s cooperating. Treat him as a displaced individual until Genius Society oversight says otherwise.”

She commanded firmly to avoid miscommunication. Hearing this, Arlan lowered his weapon and signaled for the other guards to do the same. Ben let out a sigh of relief before muttering, thankfully under his breath.

“Phew… Nearly thought this was about to result in another catastrophe.”

In a dim room on another section of the space station, lit only by flickering backup monitors, three figures stood beside each other as they listened to Asta’s transmission. Behind them was smoking lab equipment, remnants of burnt devices, and malfunctioning wires filled the air. Despite that, they were dressed in esteemed clothing, radiating the concepts of elegance and intelligence. They were members of the revered Genius Society, a group of the most brilliant minds in the universe:

The one standing on the left was a young woman who stood as though the world had paused to examine itself through her ethereal turquoise gaze. Her skin was fair, alongside long brown hair with turquoise strands loosely tied with a golden colored DNA harpin–a mark of logic. Her dark-green quipao, trimmed in brown, white, and muted gold, clung to her curves. Her fingers twitched slightly under her elbow-length gloves, distributing her weight equally among both legs as she continued listening to Asta’s transmission. This was Ruan Mei, Genius Society #81, a sweet-tempered and elegant scholar, an expert in biological sciences like none other.

The one standing on the right was more automaton in appearance, a refined man, or better to say, an intellitron, who examined the situation with a blank-slate expression, yet at the same time, expressing so much even with the limitations of his physiology. His body is composed of polished brass and steel with visible joins. He has a distinctly Victorian steampunk aesthetic as he gazes with glowing eyes and a gentlemanly visage, and scholarly elegance. He dresses in a tailored formal ensemble reminiscent of a noble intellectual: a dark tailcoat layered over a waistcoat, a neatly tied cravat at his collar, and fitted trousers, all rendered in subdued, dignified tones that contrast with the warm metallic sheen of his frame. This was Screwllum, Genius Society #76, the intellitron aristocrat who lives and is the sovereign of Planet Screwllum.

Lastly, standing in the middle was a bull-jointed puppet depicting a petite young woman. She had a slightly annoyed expression on her face, clearly due to some failure, yet that did not diminish her confidence. She had long, ash-brown hair with purple eyes that looked halfway between glowing. She is draped in a frilly white minidress under a black and purple coat that boldly exposes her shoulders. Her dark purple and white heeled boots tap on the floor with slight impatience as she, too, listens to Asta’s report alongside her peers. She is Herta, esteemed Genius Society #83; human, female, young, beautiful, attractive… She is the true master of this Space Station, who only ever appears in the form of a marionette based on her younger self, controlled by her true self at the edge of the cosmos.

Soon, Asta reported everything she knew about the situation as she temporarily put the holographic transmission on hold in an attempt to tame the situation and gain more information about everything that had happened at the Supply Zone. After a few seconds, Ruan Mei spoke up in a reflective tone of voice, folding her hands with elegant poise.

“A foreign arrival… pulled through a malfunctioning portal. That aligns with the unexpected energy recoil we detected.” She commented in neutral surprise and wonder, even for a scientist of her caliber, such a result would’ve been deemed impossible a few minutes ago.

Tapping his mechanical chin, Screwllum added in his own thoughts, brimming with both logic and the concern of its implications.

“Which implies our attempt at controlled dimensional access created an uncontrolled cross-universal siphon.”

Herta huffed, lazily continuing to tap the cold floors with her foot in her puppet body, rolling her eyes as she broke her unusual silence with annoyed confidence paired with a flat and unimpressed tone.

“Whatever. If he fell out of our portal, then he’s our responsibility now… Fine. Bring him here. We’ll interrogate the anomaly.”

She cut the transmission before Asta could conjure up a response. With that, back at the Supply Zone, Asta and Arlan escorted Ben to the Special Purpose Lab, passing by several windows showcasing the vastness of space. The emergency lights painted their faces gold as they walked. Ben took in the strange, almost foreign architecture, floating platforms, impractical railings, and puppets lying around like sleeping jellyfish.

“Whoever built this place took ‘safety hazard’ as a design goal,” Ben murmured under his breath, causing Asta to snort lightly, despite herself.

They reached the large reinforced doors of the Special Purpose Lab, which they had to slide open manually due to the power outage. Inside, only the faint glow of Imaginary Energy devices lit the chamber. Three silhouettes had awaited their arrival. Herta stood front and center, Screwllum stood tall and polished like a living machine, and Ruan Mei watched with a cold, analytic expression.

Herta took the lead by asking him bluntly while assessing everything there was about him. “You’re the stray. Explain yourself.”

Ben stopped. He wasn’t scared, almost feeling slightly nostalgic as he had dealt with similar people before. But experience didn’t stop the low and cautious expression from forming on his face as he answered them directly. 

“Name’s Ben Tennyson. I’m not from this universe. A portal grabbed me mid-sentence, and I ended up breaking your window. Sorry about that.”

He paused after introducing himself, then asked cautiously, “So you’re the ones behind the portal that grabbed me here?”

Herta followed up as she drifted closer, “If you’re here, it means our experiment worked. Just… incorrectly.”

“Understatement of the century,” He replied.

Screwllum tilted his head, studying Ben’s posture, vitals, and microexpressions. He spoke with clinical curiosity, “Your physiology is similar to that of regular homosapiens. And your arrival method is consistent with forced displacement that only the portal would've very likely caused. Yet you appear so remarkably calm.” He noted.

“Experience, lots of experience.” Ben shrugged lightly; his eyes then landed on Ruan Mei, who continued to stay back, taking notes on her holo-pad, before eventually speaking. 

“Your arrival aligns too closely with our experiment to be a coincidence. You were drawn here by the surge.” She spoke with curiosity in her gaze.

“Definitely.” He agreed. He then hesitated for a moment before turning his gaze in a way that he could see all 3 of them in his point of view.

“Been through worse. Doesn’t mean I’m thrilled. You're lucky that the person you accidentally took is well-versed in interdimensional travel.” He sighed quietly before speaking up once more, “Well, now that I’m here, I presume you want me to explain my story?”

“Well, obviously. Why else would we bring you in here for?” Herta replied, sarcasm evident in her voice.

He then explained everything: what he was doing before his arrival, the planet he was from, and how the portal had suddenly sucked him into its event horizon while he was in the middle of a meeting. The trio listened with rapt fascination, each piecing together possibilities. When he finished, Herta leaned back slightly with a sigh.

“Well, unless you know how to rebuild a multidimensional energy regulator, you’re stuck here until we fix the mess. You won’t be going home soon.” She said bluntly in a matter-of-fact tone of voice.

Ben nodded, as if having expected this response since he got here, “So I’m stranded. In space. Again.”

Ruan Mei then turned away from analyzing the holographic archives in the room and looked at him directly. “You planet, ‘Earth,’ was it? It’s not recorded in our database at all, so we’ve more or less confirmed that you're truly not of this world. That, and the fact that you don’t have a single trace of Imaginary Energy within your body.” 

The precision in her voice was quite evident. Ben could only sigh even deeper as he heard the results of the analytic report. He was really hoping that he wasn’t stranded in a foreign dimension, and that this was either a weird dream at the minimum, or displaced in his universe at the maximum. It really seemed that this time, he was truly alone.

Asta glanced at him sympathetically, knowing how hard it must be to be displaced not only from your home, but from space-time completely. However, her moment is rudely interrupted when she receives a notification through her phone that the electrical engineers have finally arrived to fix the power grid. But staying loyal to her duties, knowing what must be done, she asks permission from Herta to leave to oversee the issue in the electrical room.

“Madam Herta, we’ve called station engineers to fix the power grid. I’ll be going to oversee their work. Reports indicate that it’s badly damaged. The entire backup network is—”

 Hearing their predicament, and briefly looking around, taking the full essence of the dark room, he smirked before speaking up in playful confidence. “I can fix that.”

At his reply, they all looked at him with synchronized skepticism. Herta raised a skeptical brow. “You? Fix my station? Please. Only a genius could repair the station’s grid. It’s built on my designs.”

Ben merely brushes off her comment. He’s faced tough problems requiring genius-level engineering skills before, and fixing one of the most complex power grids of this universe in the most ingeniously complex space station in the universe barely scrapes his top 10. He lifted his wrist as the green hourglass symbol on his watch lit up. It glowed a vivid, neon green. The darkness that dominated the room let its light shine more evidently.

Seeing this, gazes of suspicion slowly plastered themselves on the geniuses’ faces. Ruan Mei became slightly surprised, even taken aback, recognizing the complexity of the technology based on the device’s composition. Screwllum's eyes become fixed on the device, analytic equations running in his head, attempting to break down its schematics with his knowledge. Herta’s eyes widened, for once, unfamiliar with a device that looked to have signs of such high-tech that she didn’t know about, so she spoke up again. 

“What… is that?” The interest in her voice has skyrocketed compared to before.

Picking up on that small clue, he grinned slightly, “My toolbox,” he said before slamming the dial.

A burst of emerald light then lit up the room, the darkness momentarily giving way to the burst of sudden light. Energy arced as it started to rewrite his form. As the light cleared, a towering crustacean-like alien stood in his place, sparking with electricity, cranial plates glowing like thunderstorm clouds. Plastered on its face was a giant static smile that didn't bother moving when it spoke.

ANOTHER EXCELLENT OPPORTUNITY TO DEMONSTRATE MY SUPERIOR INTELLECT.

It spoke with resonant brilliance in a British-like accent. The geniuses stared, momentarily stunned by what they were seeing. They couldn’t process what kind of creature they were looking at. Never have they seen something look so truly… Alien.

Asta blinked twice before asking in a confused and awe-struck manner, “...You… shapeshift…?”

The alien merely gave a brief nod before marching towards the exit, declaring in a booming voice, “DIRECT ME TO THE DAMAGED ELECTRICAL SYSTEM. MY VAST INTELLECT DEMANDS ENGAGEMENT.”

With that, Arlan then led the way for the strange alien creature. They entered the electrical room of the space station, filled with fried conduits, melted circuits, and smoking power panels that burst with electricity not too long ago. 

Assessing the situation with its enhanced intelligence, the alien cracked its claws together as bolts of bio-electricity arced forward. His cognitive fields hummed, mapping the entirety of the space station’s complex power grid system in mere microseconds. He then struck the main node with a sharp blast.

Suddenly, but slowly, lights across the station blinked, flickered, then erupted back with new life, having been breathed into them. The hum of restored power vibrated through the metal floors. Everything was back to normal now, and it had only taken the alien under a minute of engineering.

Asta, Arlan, Herta, Ruan Mei, and Screwllum all stood stunned in the newly restored luminescence. Brainstorm folded his claws behind his back with pride.

A SATISFYINGLY SIMPLE TASK. PERHAPS NEXT TIME, PLEASE PROVIDE AN ACTUAL CHALLENGE!” 

Witnessing this act of genuinely unparalleled intelligence, Herta’s puppet body twitched as she quickly regained her composure in flabbergasted indignation, something unusual from the genius, “How—?! Who—?! What are you?!” She asked.

The alien clicks its mandibles together, the eternal smiling expression plastered on its face seemed to grow just slightly more sly and wry as it turned back to look at them.

It flashed them it's everpresent wide smile, as if knowing his answer would become the foundation of much more chaos to come.