player (underplayer)

The player is the strongest of all hackers.
Player can destroy a barrier that can hold all monsters in a country, as well as destroying every barrier in every au in one tap.
If you don't want to accept his mercy or you want to fight him he will just explain to you what he wants but if you don't listen to him and just keep attacking him then he'll definitely attack back.
He is stronger than Chara (Resurrected on the path of Genocide) and Asriel (In the Form of the HyperDeath God). Fan-Art.Player's LV is 99999999, or likely more as shown in the judgement hall, where the whole page was filled with 9s.
Player used their programming skills to hack themselves into Undertale, creating an Amalgamate as their vessel for their SOUL.
Under mysterious circumstance, the original copy of Underplayer was removed from the creator's account, along with the closure of the English translation's Tumblr page. Fortunately, the original image panels were restored and archived online.

Undertale Characters
Frisk
In this AU, Frisk represents another player from the outside world entering PLAYER's world. Eventually, PLAYER takes the reset button from Frisk, which prevents players from possessing Frisk and thus, Frisk acts as their true self.

Sans
Sans is mostly the same, but because PLAYER jumps through worldlines and not timelines, Sans cannot remember previous runs.

Flowey
On their first run, PLAYER takes Flowey with them to Snowdin before they are intercepted by Sans. After PLAYER fails to break the barrier, they go back to their spot in the Ruins to greet Frisk 1 month later.

Gaster
In this AU, Gaster acts as a guardian against major changes to the Undertale story. This prevents PLAYER from breaking the barrier early, moving past the endings, and undoing genocide Frisk's actions, to name a few things.

Added Characters:PLAYER
The player is the lead protagonist of this AU. They're based off of a real life player, whose unsatisfied with the endings of Undertale; and thus entered the world itself to create a better outcome.

Locations
Undertale Locations
Ruins, Snowdin, Waterfall, Hotland, New Home
AKA the Underground in general. When PLAYER is not trying to reach the ending, they spend most of their time in waterfall with Sans and Flowey or Asriel.

Last Corridor
Sans immediately confronts PLAYER there due to them entering Snowdin with 99999999 LV. However, Sans eventually realizes that PLAYER won't fight and that the LV can be explained, so he agrees to stop fighting.

Miscellaneous
Introduces the concept of a "world line" -- that is, a set of all possible timelines in Undertale. Every possible FUN value has its own associated world line. This concept is similar to the general concept of an AU.
PLAYER cannot jump between timelines, only world lines.
PLAYER has the power to modify Undertale's code, but if they attempt to alter the story massively, they will be kicked out of their current world line. This is thought to be the cause of Gaster.

The Power to travel through Worldlines(AU’s)
It is stated in the article linked above(provided by the creator of underplayer themselves), that 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 omniversesThe 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. (See weakness below.)

Gaster was Player's weakness due to the fact that Gaster will always kick Player after they finish the game or change the Worldline massively.

However, Player managed to circumvent it by locking Gaster in his room so Gaster can't kick Player anymore now because Player has locked the whole room.

Character Universe is UnderTale. Do not think that UnderPlayer is an Alternative Universe where only the Player exists. According to the canon, a player appears in the UnderTale world, trying to become an absolute friend to everyone.Soul
The soul of Player is the personification of darkness and determination. The black heart is the personification of a small part of the darkness that gave the Player such a huge level. The red heart that is inside the black is the personification of determination. With the help of determination, the Player can do a reset, action, mercy, and attack. Also, because of the red soul, the hacker may survive.

They are programmer\hacker with an empty heart; Not a single ending of the game suited them, in the eternal search for a better ending for themselves; Uses their soul to jump through space; Uses program code to communicate with them; The master of a tremendous power of decisiveness, which they cannot always control. Always wants to seem strong in front of others, but in the end remains a monster in the eyes of others; Poorly versed in color gamut adjustment; Always does only what they sees fit. Not on the side of evil nor good. The main goal for them is to find advantages for themself.

Then Chara appears in front of the player, which the Player abruptly replaced. Next is the exchange of discharges. Having exchanged his reset with the Player reset, the Hacker makes a blow that kills Frisk, as at the end of the Genocide. The button was a reset that led to the alternative HorrorTale universe where the sinner will spend terrible times. Reset Frisk himself makes a choice. Having reached the end, Frisk passed the pacifist completely. The Player replicated a monster soul for Asriel and a human soul for Chara so that they could both live. Then the player makes a reset, after which he enters the room where Gaster was, and puts him the final ultimatum.

It all starts with the fact that our hero appears on the flowers, as the children did. Like everyone else, the Player meets Flowey, who, as always, wanted to appear to the stranger as a “friend”, so that he would later nastily stab him in the back. But our hacker is not easy. Having completed all the endings, they already knew perfectly well that, in fact, this flower is evil itself. Grabbing the stem of Flowey, he remembered everything that happened in all time lines. Having remembered everything, Flowey wanted to insult the Player, but the Player frightened him, saying: “Don’t dare to talk to me like that, otherwise I will tear out and recount all your petals.”

Then they walked along the Ruins, after which they said goodbye to Toriel and left the Ruins. And so it all went to a snowy location. The Player meets a joyful skeleton, who held out his hand. Sensing the level of the player, Sans made an attack, but unfortunately the skeleton did not hit. Then the player and the skeleton appear in the courtroom, where the person explains that he, how he not knows everything and where he got such Level (known as L.O.V.E. or Level Of Violence.

But evil does not sleep. Another Player started a Genocide run, simultaneously managing Frisk as a puppet. The Player stops for a while, after which he is thrown out of the world. Unfortunately, Chara took control of Frisk, telling the brothers that this world would soon be erased. So everything went until the royal guard gathered in the courtroom. Sans, Mettaton and Undyne. They tried to stop Frisk, but nothing came of it. Further, the Frisk, which was controlled by the player, makes a blow to Sans, thereby disabling the skeleton. It would seem that already death takes the skeleton, but the Player returns again, calling for green friendliness pellets, which quickly flew to Sans and healed him. Further, Frisk makes a blow to Asgore, killing him and ending the genocide (Flowey is killed in the Ruins).

Key Personality TraitsDetached and Goal-Oriented: They treat the game world like a sandbox, focusing strictly on achieving a "perfect ending" or manipulating outcomes without genuine emotional weight initially attached to the characters.Arrogant and Naive: They act on the belief that their outside-world perspective makes their actions inherently correct, often ignoring the unintended psychological trauma or chaos they cause the underground inhabitants.Reserved yet Ambitious: They tend to keep to themselves and hide an empty, hollow core beneath a powerful exterior of code-manipulating confidence.Unpredictable: Operating outside standard monster morality, they are neither purely benevolent nor malicious—instead acting entirely on whatever advantages or narrative goals suit their current whim.she is a Level Multi Threat/Multiversal(Highball).her Marital Status is Single and they Pronouns are she/they.

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, but this was not shown in the comic. Also under the eyes has red ovals, which are possibly cheeks

Deltarune, the "Vessel" is the custom character you piece together during the game's opening sequence (the "Goner Maker"), which is promptly rejected by an unknown voice who states, "No one can choose who they are in this world," before forcing you to control Kris instead.The Opening Sequence & RejectionThe Goner Maker: At the very start of the game, an anonymous voice (widely associated with W.D. Gaster) has you select head shape, torso, eyes, hair, and favorite things to build a face-less, grey humanoid.Discarding the Creation: After you finish naming the Vessel and your self-insert "creator" name, a second voice interrupts, discards your custom creation into the dark, and transitions the game straight to Kris's awakening.The Red SOUL: The player's red SOUL is subsequently forced into Kris's chest, setting up the core dynamic where you pilot Kris against their apparent will.In Deltarune, the player begins by designing a faceless "Vessel" in a sequence labeled the "goner maker". This creation is abruptly rejected by a mysterious voice stating "no one can choose who they are in this world," forcing the player to control the human teenager Kris instead.Creation and RejectionThe Goner Maker: At the very start of the game, players pick head shapes, torso types, eye colors, and favorite things to build the Vessel.The Discard: A second voice interrupts the process, discards your custom creation into the void, and binds your red SOUL to Kris instead of your custom character.

Connection to KrisInvoluntary Host: Unlike a blank slate, Kris is an independent person with their own history, family, and strained relationship with the player's SOUL.SOUL Removal: Throughout the game, Kris periodically rips the red heart (SOUL) out of their chest, showing a desire to act outside the player's direct control.Community TheoriesFuture Return: Many fans believe the discarded Vessel will reappear or become important in later chapters of the game.The Prophecy: Dialogue and text clues from newer chapters reference ideas like a "cage of human parts and soul," fueling debates over whether the player and Kris were ever meant to be paired together.

The vessel in Deltarune is the custom character you build during the Survey Program introduction at the very beginning of Chapter 1. A mysterious voice (presumed to be W.D. Gaster) guides you through choosing its head, torso, legs, favorite things, and name, before abruptly discarding it with the statement: "No one can choose who they are in this world." Instead, the player's soul is forced into Kris.Creation and CustomizationAppearance: You select a head (8 options), body (6 options), and legs (5 options).Personality traits: You answer choices regarding its favorite food (e.g., sweet, pain), blood type, color, and an assigned "gift" (e.g., kindness, ambition).Naming: You give a name to the vessel and a separate name to the "creator". Typing specific names like SANS or PAPYRUS yields unique text, while naming the creator GASTER crashes the game.Significance and TheoriesSaved Data: Even though the game tells you the vessel is discarded, the exact customization choices you make are saved directly in your save file data. This heavily implies it will return later in the story.Community Speculation: Fans widely theorize that the vessel you created will eventually become accessible or used later in the series—perhaps as a final body, an adversary, or something found inside the mysterious town bunker.Customization PartsHead: Choose from options that alter the shape and facial layout.Torso: Select configurations like default, short, or baggy sleeves.Legs: Build the lower half, which generally appear as thin or stylized stick-like shapes.Face/Hair: Pick distinct eye styles, hair options, and clothing aesthetics.Color and ThemePalette: Entirely greyscale/monochromatic during the Goner Maker sequence.Status: Though discarded by a mysterious voice ("effectively" replaced by Kris), your customized appearance data is permanently saved in the game's save files, leading to heavy community speculation about its return.

side note:your soul in your own body aka the vessel.

Underplayer is an Undertale alternate universe (AU) and fan comic created by Yunan. It follows a real-world entity called "The Player" who hacks and inserts themselves into the game code with the ultimate goal of achieving a perfect, happy ending where they befriend every monster.Core Concept and PlotThe Protagonist: The Player is a separate entity from Frisk and Chara. They come from the real world, treating Undertale as a game they have mastered and wish to alter.The Goal: Instead of standard routes, the Player wants to force a true, flawless happy ending by interacting with timelines and restoring monster memories from different paths.Unforeseen Consequences: Interfering with the game's code and memories causes chaotic reactions. Characters like Sans react with extreme hostility and try to stop or kill the intruder because they remember past timelines and perceive the Player as a dangerous anomaly.Key Abilities of the PlayerHacking Code: The Player can manipulate game data, use code-based attacks, and dodge high-damage strikes like Gaster Blasters.Amalgamate Vessel: Their body and powers are formed using the combined code and traits of various monsters.

Underplayer is an Undertale fan comic created by the user Yunan where a real-world human player hacks into the game's code to break the loop and achieve a true, perfect happy ending for everyone.Core Premise & IdentityThe Protagonist (PLAYER): Represents the real-world person playing the game. Tired of standard outcomes, they use programming skills to inject a physical form into the Underground.The Vessel: Their physical body is an amalgamate made from monster and character code (including traits from Flowey and others), housing a sliced piece of the real-world player's actual soul.The High LV (99,999): PLAYER's absurd Level of Violence does not come from killing Undertale monsters, but from accumulated survival experience across various other violent video games played in the real world.Key Mechanics & RulesWorldlines vs. Timelines: PLAYER navigates via "worldlines" tied to Undertale Fun Values rather than standard chronological timelines, allowing them to shift across alternate setups.WD Gaster's Role: Gaster acts as a systemic guardian/enforcer who tries to wipe out or overwrite PLAYER whenever they attempt massive code-breaking changes (like shattering the barrier prematurely).Frisk and Chara: Frisk eventually acts as an independent entity separate from real-world player control once PLAYER steals/neutralizes the reset button, while Chara often resists external manipulation.