Underplayer

It all started when the Player woke up in a patch of golden flowers — not as a child, but as themselves. They already knew this world, every pixel, every line of code. They’d played every ending, memorized every kill. So when Flowey popped up with that fake smile, the Player didn’t flinch.

Before the flower could even say “Howdy,” the Player’s hand snapped out and closed around his stem.

“Try it,” the Player said softly. “I know every reset, every timeline. I’ve seen you beg, I’ve seen you gloat. One wrong word and I’ll pluck every last petalyou have.”

Flowey froze. For the first time, he wasn’t the one in control.

The Player moved through the Ruins like a ghost — no surprises, no fear. They spared Toriel, not out of mercy, but because they were focused on something bigger. When they stepped into the snow, Sans was already there, hand extended, smile tense.

He sensed the LOVE — not from violence in this run, but as a stain from countless others. Sans attacked, but the Player dodged. They’d fought him a hundred times before.

In the judgment hall, Sans stared them down. “Where’d you get that level, kid? You haven’t hurt anyone here… but you smell like genocide.” The Player just smiled. “I remember. All of it.”

Then — interference. Another Player, somewhere else, hijacked the timeline. They seized Frisk like a puppet and launched a Genocide run. The real Player was forcibly logged out, screaming into the void as Chara surfaced, grinning through Frisk’s eyes.

“This world will be erased,” Chara hissed.

The royal guard assembled — Sans, Undyne, Mettaton — but they were outmatched. Frisk’s blade sliced through defenses, and Sans fell, his HP dropping to zero. Just as his light was about to fade, the Player tore their way back in. With a wrench of code, they summoned a hail of green friendliness pellets — healing, not harming — and Sans gasped back to life.

But it was too late to stop the run. Asgore fell. Flowey was already dust in the Ruins. Chara appeared, offering the world in exchange for a soul.

The Player didn’t bargain. They overwrote Chara’s reset command with their own, crashing the system into a hard reboot. Frisk’s body shattered like glass. In the silence that followed, the Player hit RESET — but not to the beginning. They sent the other Player, the genocider, spiraling into the HorrorTale AU, a nightmare dimension where they would suffer.

Then, with full control restored, the Player guided Frisk through a True Pacifist ending — but changed the finale. Using hacked soul data, they replicated a monster soul for Asriel and a human soul for Chara, giving both a second chance.

As the credits rolled, the Player executed one final reset — not to the start, but to a gray door that shouldn’t exist.

Inside, surrounded by whispers and static, Dr. Gaster looked up.

The Player stepped forward. “No more experiments. No more fragments. I’m not a puppet, and this isn’t your game anymore.” They placed a modified Save file on the table between them. “Here’s the new rules.”

Biography Name: Underplayer (or Player) Gender: Unknown Species: Human/Hacker Height: 4ft Weight: 120lbs Age: Technically ageless but 35 Eye Color: Red Hair Color: Red Skin Color: Grey Physical Appearance: Has large breasts twice as bigger than her head, thick thighs, curvy body overall and a ass twice as big as her tits Appearance: The player is dressed in a black suit, vaguely reminiscent of a dress. This “dress” covers the Player's knees. On this very suit, like Frisk or Enchantment, there are red stripes. From under the suit, you can see black pants and dark brown shoes. The Player's hair is red. Their white eyes are black and their iris is red. Unlike the above listed Frisk and Charа, the Player has gray skin. Since this character has the ability to manipulate the game, they can change their appearance. Also under the eyes has red ovals, which are possibly cheeks. Personality: They are a programmer without a program, a hacker without a home. They’ve run every ending, met every character, seen every death and rebirth — and none of it ever filled the hollow space where their heart should be. The Pacifist ending felt like a lie. The Genocide ending felt like a chore. They aren’t looking for good or evil. They’re looking for an ending that means something, just once.

Their power is absolute — and absolutely flawed. They can manipulate the code of reality itself: glitch through space using their soul as a catalyst, overwrite attacks, even summon entities that shouldn’t exist. But their control is like holding a live wire — the more they grasp, the more it burns. Their "tremendous decisiveness" isn’t a blessing; it’s a reflex. Once they choose a path, the code locks in, and changing course requires tearing reality apart. Sometimes they break more than they fix. They don’t always mean to be cruel. But in a world made of fragile data, even a debugger can crash the system.

They speak in a mix of glitch and gesture — elegant, efficient, and alienating. Their "voice" is a blend of borrowed dialogue fragments, strings of code, and visual static. They can talk normally if they concentrate, but under stress, they slip into syntax and error logs. It’s not to be cool — it’s because they’ve spent so long in the save files that they’ve started to think in commands. To others, it sounds like noise. To them, it’s the only language that doesn’t lie.

They wear strength like armor, but everyone sees the monster underneath. They posture, they dominate, they hack their way through problems — not because they feel strong, but because they’re terrified of being seen as weak. Yet no matter how many times they save the timeline, the monsters look at them and see a glitch in the form of a person. Something hollow. Something wrong. In their drive to find a better ending, they’ve forgotten how to be anything but a force of will.

Their morality is a grayscale they don’t bother to adjust. They’re not evil. They’re not good. They’re pragmatic. They’ll spare a monster if it gets them closer to their goal. They’ll kill one if it’s more efficient. They don’t relish cruelty — they’re just so used to resetting that consequences feel like temporary variables. Their main goal is to find advantages, because advantages are the only things that ever last between timelines. Friendship fades. Memories reset. But a well-placed backdoor in reality? That persists.

Beneath it all is a terrifying truth: They don’t know what they want. Only that they haven’t found it yet. And they will rewrite the universe until they do.

<Powers/Abilities> The Power to travel through Worldlines(AU’s) They have the ability to travel through worldlines. In the underplayer universe, to simplify it, a worldlines is basically an AU. Simply put, the player has the ability to travel through alternate universes even in omniverses

The Power to change the plot of Worldlines(AU’s) It is stated that the player has the ability to change the plot of worldlines. This means they have the ability edit any part of the game’s code. Items, places, stats, characters, personalities. They have one major flaw to their abilities however.

Information Manipulation (Their nature as "The Player" gives them virtually full control over the coding and data that makes up Undertale's fiber, this includes being able to mess with the data encryption to change functions and rules), Plot Manipulation (Able to retroactively change the plot of Undertale and change how it progresses, such as changing the endings, altering events and even preventing endings that result in Timeline Destruction), Non-Corporeal and Possession (Normally exists without any concrete body and instead, manifests avatars in order to interact with reality), Time Paradox Immunity (Unaffected by resets and true resets), Time Manipulation, Time Travel, Timeline creation and destruction, Soul Manipulation (Able to interact with and attack souls. Restored Flowey's soul, causing him to change back into Asriel), Ability to SAVE and LOAD, Life Manipulation (Capable of bringing back dead people, including Frisk and Papyrus), Reality Warping, Duplication (Able to duplicate themselves countless times and place them in other timelines), Void Manipulation (Entered and can interact with Gaster's Room, which is a location that sits outside of reality and doesn't exist), Regeneration (Low-Godly), Immortality (Type 9, Killing The Player's avatars won't effect the actual entity itself, who resides in the real world), Dimensional Travel (Can travel to different timelines and AUs), Biological Manipulation (Through alteration of data, PLAYER can change the very body features of a character and their functions), Non-Physical Interaction (Capable of effecting nonexistent and incorporeal beings such as Gaster). Resistance to, Reality Warping, Existence Erasure, Information Manipulation and minor to Memory Erasure. Immunity to Soul Manipulation, Fear Manipulation and Empathic Manipulation (Due to having no soul, can't feel true emotions. Also unable to feel fear of any kind)

Intelligence: Gifted (Is an expert hacker, having the ability to mold and shape the coding and data that makes up Undertale to a virtually limitless degree. Has awareness of and knows of other realities, AUs and even other series such as Legend of Zelda, Final Fantasy and upon others. Considered smart even by the standard of Sans and Alphys, who are treated as two very intelligent minds)