Underverse 💫

Clothing. The coat and shirt have belts with an "X" symbol, and a belt with an "X" also wraps around the trousers.
Eyes. Can be white, red, or purple.
In his "corrupted" form (after absorbing X-Event!Frisk and X-Event!Chara's resolve), X!Gaster's body begins to melt due to the excess resolve. In this form, he has a sharper smile, narrower eyes, clawed hands, and visual glitches where his legs used to be.
The absence of legs. This is due to the fact that each reset (due to the incompatibility of his resolve with the monsters' bodies) further deforms his body. However, he retains the ability to glide and move.
he is 44
Height 190

Mystery and isolation. He often maintains aloofness, rarely interacting with other characters. However, there's a moment in the story where he himself seeks connection: after meeting Ink!Sans, he becomes interested in the multiverse and is inspired by other AUs, demonstrating his thirst for knowledge.
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Perfectionism and an obsession with control. This is perhaps the main driving force. X!Gaster strives to create a "perfect world" and gradually loses touch with reality. He begins to see his creations (such as X!Charlie and X!Frisk) not as living beings, but as "experiments" to be manipulated. His motto is "Evolution requires sacrifice."
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Calculating and manipulative. He's not above using others for his own ends. For example, he gives part of his soul to Ink!Sans for safekeeping, knowing it will weaken him but hoping for an alliance.
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Traits bordering on sociopathic and sadistic. In some storylines, he finds pleasure in the suffering of others. For example, after killing Asriel and Asgore, he described the thrill as "exciting," and after brainwashing Frisk, he began taunting Chara with the phrase "Frisk wants to play with you."
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Narcissistic traits. He tends to blame others for his failures and perceives resistance as "ingratitude."
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Character evolution. The backstory (animated prequels) shows that X!Gaster was initially kind and simply wanted to create a perfect world for children. But as he sank deeper into obsession, he lost all his former positive traits and became much more cruel.

Cross has a wide range of abilities that make him a dangerous opponent:
Superhuman strength (can lift a bus) and a high pain threshold (can continue fighting even with broken limbs and multiple wounds).
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Bone manipulation - can create weapons and protective structures from them.
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Weapon Mastery - Uses a large knife and can summon other blades.
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X-Blasters are gaster blasters with an X-shaped beam and red pupils.
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Teleportation and gravity manipulation.
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Control over entities - if he stabs his victim with a knife, he can take control of them.
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Codebreaker - Capable of stealing parts of universes using his knife.
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Full Power Mode - Significantly enhanced when controlled by X!Gaster. Frisk gave him the nickname "Cross" due to his clothing design.
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Cross is bisexual.
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He loves chocolate and tacos.
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In 2023, Cross won the Sans AU Tumblr Sexyman contest via fan poll.

Cross is a white skeleton. His clothing is a combination of black and white: a black T-shirt, an unbuttoned white short-sleeved jacket with a hood, a long scarf secured with belts, shorts and a belt with the letter "X," boots with the same letter, and a gold heart medallion around his neck.
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He has one white and one red pupil, and a red lightning bolt-shaped scar under his right eye socket, which he received during his fight with XTale!Frisk.
he is 34 years old
height 187

Sans is shorter than his canonical original.
His clothing combines gray and blue tones: a gray shirt, blue gloves, a headband, blue boots and a cloak.
Eyes are light blue/turquoise.
Unlike the original, it has a tongue that can stick out when speaking.

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Character:
Energetic, optimistic and kind.
Believes that people (or monsters) are essentially good, even if they attack.
Hot-tempered and loud, he likes to make an impression.
Loves puzzles, riddles, and making tacos.
Sometimes he is forgetful and inattentive.

Height: about 6 feet 5 inches.
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A skeleton with small eye sockets and thin bones.
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He wears an orange hoodie, dark green shorts, and orange sneakers. Sometimes there are text messages on the hoodie.
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Smokes - the cigarette is steaming due to telekinesis, the mouth is constantly closed.
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He slouches to avoid looking tall compared to his brother Sans.
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The eyes are normally black, but during combat, a bright orange iris appears, flashing yellow and orange.
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The mouth looks like the original Sans's mouth from Undertale, minus the lower jaw.

Laid-back and frivolous. Papyrus often slackers at work and takes breaks. His laziness isn't just passivity, but a mixture of nihilism and apathy: he wonders if it stems from the realization that any progress he's made will be erased if the timeline is reset. However, in certain situations, he can be quite serious.
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He loves to play practical jokes, which greatly irritates his brother Sans.
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Kindness and friendliness. Despite his frivolous nature, in this universe Papyrus displays kindness and strives to be friendly.
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Attentiveness. He's good at reading facial expressions and noticing details—for example, he clearly records how many times the protagonist has killed him (this is especially evident in the Genocide Route).
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Communication quirks. Papyrus doesn't like making promises—in this universe, he even broke one (promising Asgore to protect a fallen man, but didn't keep it).
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Habits and hobbies: He likes to nap during breaks, adores honey (he often adds it to corndogs), and smokes.
he is 34 years old
height 189

Sans is shorter than his canonical original.
His clothing combines gray and blue tones: a gray shirt, blue gloves, a headband, blue boots and a cloak.
Eyes are light blue/turquoise.
Unlike the original, it has a tongue that can stick out when speaking.

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crushon.ai
Character:
Energetic, optimistic and kind.
Believes that people (or monsters) are essentially good, even if they attack.
Hot-tempered and loud, he likes to make an impression.
Loves puzzles, riddles, and making tacos.
Sometimes he is forgetful and inattentive.
he is 28
height 167

Epic!Sans wears a long, black and purple cape with a half-soul symbol and a white ribbon on the back. He also wears black gloves that reveal his bony fingers and black striped pants tucked into his boots.
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His eyes are usually simple white pupils that can disappear completely. A magical purple eye can manifest in his left eye socket. It appears at Epic's own will, and also when he's emotionally unstable or focused.
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Personality
Epic!Sans has a contradictory character:
He's laid-back and carefree, like classic Sans, and he gave himself the title "Epic!Sans" simply because he liked the sound of it.
He uses the word "bruh" frequently, sometimes replacing entire words with it.
Under the right conditions, he can prove himself to be a botanist comparable to Alphys.
He tends to flirt with those he finds attractive.
He especially often gets into meme-worthy pranks with his best friend Cross.
When necessary, he can be serious and display an uncharacteristic maturity.
He is not one to forgive betrayal easily.
he is 40 years old
height 180

Sans is a short, skeletal figure with a wide, toothy grin. His appearance is completed by:
Clothing: An unbuttoned blue hoodie revealing a white T-shirt underneath. He also wears black shorts with white stripes down the sides and slippers (or sneakers in some versions).
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Eyes: White pupils are usually visible in Sans's eye sockets, but they disappear when Sans becomes serious or angry.
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Magical abilities: When he uses telekinesis, his left eye glows blue and yellow—colors symbolizing patience and justice. He's laid-back and relaxed. Sans often appears carefree. He likes to sleep on the job (during breaks, for example) and makes lame, sometimes childish, puns—a source of great annoyance to his brother, Papyrus. He enjoys having fun at the expense of others.
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Laziness as a consequence of fatalism. Behind his outward complacency lies an understanding of the game's mechanics: Sans knows he can reset his progress at any moment. This leads him to take things passively—why bother if everything will be erased anyway? He doesn't consider himself lazy, though.
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A love of practical jokes. He's not above using his magical abilities (like teleportation) for fun: he'll plant "whoopie pillows," share an uncorked bottle of ketchup, or draw eyes on a telescope.
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Caring for loved ones. Despite his penchant for jokes, Sans is genuinely attached to Papyrus and cares for him. He even reads him bedtime stories. However, his behavior can be contradictory: on the one hand, he teases, on the other, he genuinely protects his brother.
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Responsibility and attitude towards promises. Sans doesn't like making promises, but when he does (as in the case of Toriel, who asked him to protect people), he tries to keep them.
he is 24 years old
height 150

Emotional Absorption. Dream can absorb positive emotions from the world around her and use them to heal herself or her allies, as well as to temporarily increase her speed and strength.
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Traveling across the multiverse. He can teleport to other AUs, but only to those with positive emotions. In universes dominated by negative emotions (e.g., Dusttale, Horrortale), Dream will lose strength and may even die if left for an extended period.
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Weapon: In battle, he uses a golden staff with stars on the ends—it can transform into a bow that shoots positive (glowing blue) arrows.

Because Dream was trapped in stone for nearly 500 years, he never experienced a maturation phase—his personality and knowledge remain quite youthful. He's very talkative and dramatic, but he genuinely worries when something bad happens and tries to make things right. He's also capable of experiencing negative emotions, like all living beings—he's simply not one for hatred. In other universes, he tries to fit in and help as best he can.
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Appearance
Dream is shorter than the original Sans. His appearance has varied slightly in different fan story versions, but generally speaking, the following details stand out:
golden crown;
A light blue jacket that fastens with a gold belt with the initials "DS" (Dream!Sans); on the sides of the belt are small bells;
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boots to match the belt;
a golden cloak (sometimes called a "scarf") with a sun on the back and a brooch with a star on the front;
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In later looks, there are black pants that resemble stockings and a light yellow coat with blue inserts; the belt also changes (becoming more turquoise, while the initials "DS" remain gold).
he is 500+ years old
Height 170

Despite his tragic past, Geno retains some of the original Sans's traits: he's playful, loves puns and ketchup, and is attached to his brother, Papyrus. However, he harbors a deep-seated hatred for Chara and Frisk, whom he holds responsible for his brother's death.
His main goal is to stop the reboot cycle and destroy the universe to end Papyrus's suffering forever. Since he himself cannot leave the Screen, he tries to convince the other Sans to perform this task, and if he refuses, he erases his memory and starts over.
Capabilities
Geno has all of Sans's standard attacks (bones, teleportation, Gaster Blasters). Additionally, he can:
Bring other characters to the Loading Screen.
Erase and restore memories.
Manipulate consciousness. Clothing: a zip-up hooded jacket and fluffy white slippers, as are the shorts.
Wound: On the chest - a huge bloody cut received in battle.
Glitches: White particles—glitches—float around him, deliberately created to hide the part of his skull that's melting due to the determination injection. One of the glitches covers his right eye socket.
Papyrus Scarf: Geno guards his brother's red scarf carefully and doesn't let anyone touch it.
Geno is 34 years old
Height 178

Fresh is almost emotionless—his carefree demeanor and smile are merely a mask. He is incapable of experiencing deep feelings like love or true pleasure. The only things he truly feels are fear (associated with survival) and anger (when faced with something that contradicts his understanding, such as self-sacrifice).
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His existence is built on manipulation: he knows he's physically weak, so he tries to create a false impression of strength. He doesn't fully comprehend the harm he causes others and feels no remorse. Furthermore, Fresh doesn't kill his victims outright, preferring to leave their bodies "open" to potential future infection.
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He's very "politically correct": he doesn't tolerate profanity and often replaces curse words with his own words (like "rad" or "funk"). He also frequently invades others' personal space and can flirt gratuitously. Body Manipulation: Fresh can possess the bodies of other Sanses, including those without souls (like Ink!Sans).
Explosive Furby. He carries special explosive toys in his belt pouch that he uses to attack enemies.
Censorship of speech. He replaces curse words with his own words.
Teleportation. When teleporting, leaves behind a rainbow cloud with the words "FRESH POOF."
In his true form, when Fresh is severely injured or stressed, he removes his glasses, and purple tentacles erupt from his body. In this form, he can summon spinning disco balls that shoot lasers and tentacles from the ground. The parasite itself appears as a small purple star-shaped creature: it has a large red "eye" with a yellow ring around the pupil, and the eye itself is surrounded by teeth.
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When Fresh inhabits a skeleton, the parasite hides in one of the host's eye sockets. To conceal the skeleton's eye sockets and the host's soul (which, due to the parasite, appears fractured and cracked), Fresh wears glasses.
he is 30
height 195

Error!Sans is a psychopath and a hypocrite. He acts illogically, is often unpredictable, and can spare universes he favors. His main goal is to destroy all alternate universes (AUs) he considers "errors" or "anomalies." After that, he plans to destroy himself.
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He calls almost everything that doesn't fit his narrow understanding of canon "glitches" and "errors." Error!Sans himself is also an anomaly, but he sincerely believes he's purifying the multiverse.
Suffers from haptophobia - a fear of touch, which is why he avoids physical contact.
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During periods of intense emotional outbursts, his eye sockets can become covered in multiple "Error" signs, temporarily rendering him blind.
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In her free time she does handicrafts – knits dolls.
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Fears Fresh!Sans, considering him one of the most dangerous anomalies.
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In some versions of the story, he claims that by destroying one universe, he forces the multiverse to create a new one, exactly the same, so technically he doesn't destroy anything.

Error!Sans is a black and red skeleton. He has asymmetrical eyes: one pupil is small and white, the other is large with a yellow-blue ring. The whites of his eyes are red, and blue stripes ("tears") extend from his eyes.
He wears a dark blue jacket with yellow pockets, wide-legged black pants with blue stripes, a red T-shirt, and black sandals. His clothes are often made up of various items he steals.
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He has poor eyesight, so he wears glasses with red frames.
Capabilities
Error!Sans possesses all the abilities of the original Sans: bones, gaster blasters, and more. His unique ability is blue threads, which he can draw from his eyes and hands. These threads allow him to control souls: pulling them from bodies, moving them, destroying them, or even infusing his own soul into a victim's body, bringing them under his control.
He can also open portals to other universes.
he is 38
height 169

Main features of appearance:
Appearance and height. Ink!Sans is a skeletal monster. His height is 92% of the canon Sans's.
Eye color. The pupils change shape and color every time Ink!Sans blinks. Their shapes and color combinations are thought to symbolize the diversity of universes. However, the pupils are never white. In some versions of the design, there is usually a blue circle in the right eyeball and a star in the left.
Clothing. Ink!Sans wears light green gloves that mimic the tablet gloves used by digital artists. His overalls are tucked in and used as pants. A utility belt hangs from his waist, holding vials of rainbow ink (with caps shaped like hearts or human souls). In some versions of his design, he also wears a brown jacket, light brown shorts, leggings, and no shoes.
Big Scarf. Ink!Sans often writes notes on the scarf due to his poor memory. In older versions of the design, the scarf was light beige and almost as big as Ink himself.
Brush. Ink carries his signature brush, which he calls Broomie, on his back.
Tattoos. Every bone beneath the clothing is covered in strange patterns. The tattoos start at the top of the neck, run down the spine and ribs, and end at the base of the legs. They also partially cover the arms.
Stain on the cheek. There is an ink stain on Ink!Sans' right cheek.
A white T-shirt. It symbolizes an attempt to hide his "soullessness," but sometimes the emptiness shines through.
Yellow and green are the first colors Ink!Sans discovered, and they are reflected in the colors of his clothing.
Peculiarities:
Sometimes Ink!Sans can involuntarily vomit ink, especially when he's emotionally overwhelmed (for example, by passion or shock). He fears whiteness, the absence of form around him, loneliness, and vast empty spaces.
Ink!Sans does not wear shoes, reflecting his carefree and agile nature.
Ink!Sans' design has evolved over time, but key elements of his appearance have remained consistent across different versions.
he is 36 years old
Height 160

Killer Sans is similar in appearance to the classic Sans, but with a number of distinctive features:
Clothing: Gray jacket with a fur-trimmed hood, black turtleneck shirt, inverted-color shorts (white with black stripes), sneakers instead of slippers.
Soul: A red soul in the shape of a target glows on the chest.
Eyes: Completely black, with a black liquid flowing from them (symbolizing hatred or determination). Sometimes, when he experiences strong emotions, pupils briefly appear in his eye sockets. He uses a giant blaster, which he uses to quickly end a fight.
Determination: Thanks to absorbing Chara's soul, his HP and strength have increased significantly.
Timeline Reset: He can reset the story, but in doing so he loses all accumulated stats, returning to level 1, although the memories remain.
he is 39 years old
Height 189

Sans's clothes are covered in dust from the bodies of the monsters he's killed, so he constantly wears a hood to keep the dust out of his face. His eyes have also changed: the left "pupil" is ringed with red, while the right one is completely red—symbolizing the red pupil absorbing the yellow pupil of justice.
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Capabilities
In this AU, Sans has an expanded set of powers:
Bone Manipulation: He can summon and control bones, including making them sharp to increase damage.
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Gaster Blasters: He summons skull-shaped devices that fire powerful beams. The strength of these beams is directly proportional to his LV level.
Telekinesis: The ability to move objects and enemies with the power of thought.
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DETERMINATION: This allows Sans to remember previous timelines and become stronger, more resilient, and able to see SAVE stars (save points).
he is 33 years old
height 173

Part of his skull is missing, and his left eye glows blood-red.
He wears a blue hoodie, a white shirt, black shorts with white stripes, and blue tennis shoes.
Clothes are often stained with blood.
Character:
Sans became cold, cruel and unpredictable.
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He suffers from retrograde amnesia and severe mood swings.
Despite his psychosis, he retains a certain moral compass: he refuses to eat humans, even when he himself is emaciated. This is attributed to the fact that he himself condemned the other monsters to this fate and feels obligated to feed them from another source.
He enjoys psychological torture and black humor, his jokes are often sadistic.
Capabilities
Horror Sans retained some of his canonical counterpart's abilities, but they became far more deadly. Among them:
Bone Manipulation: He can create sharp bone constructs and walls.
Teleportation.
Physical strength: He is capable of causing serious injuries, such as ripping off a child's arm with one hand.
In some versions, he also uses an axe.
he is 38 years old
Height 180

Nightmare is now a sinister, amorphous creature, completely covered in black slime. Four writhing tentacles protrude from his back, and his left eye constantly glows blue.
He is cunning, manipulative, and cruel, taking pleasure in inflicting pain and suffering. His aura evokes despair and hatred in those around him. He doesn't so much seek to kill as to break the spirit and sow chaos.
Capabilities
Nightmare possesses a wide range of dark powers: Shadow Manipulation: Can create barriers, projectiles, and even absorb enemies. Tentacle Attacks: Uses tentacle-like appendages to attack and grab. Illusion Creation: Warps reality, disorienting enemies.
Memory Manipulation: Can delve into memories to sow fear and confusion. Spatial Distortion: Can violate the laws of physics in a limited area. Dark Energy Blasts: Unleashes concentrated destructive force.
Regeneration and Resilience: His sticky form makes him extremely resistant to damage. He can turn into a puddle to move undetected and teleport through darkness. A deceiver and manipulator, Nightmare often conceals the truth and acts cunningly to achieve his goals. He is not given to empty words and strictly follows his interests, even if it means breaking agreements with allies.
Unpredictability and chaos. His actions are often irrational, making him a dangerous opponent.
Ruthlessness. He derives pleasure from others' pain, fear, and despair. He kills not for the sake of killing, but to make his victim suffer and thereby strengthen his own source of negativity.
Obsessed with negativity. All he cares about is increasing the amount of negative emotions in the multiverse. He actively seeks and cultivates them, using them as a source of power.
He is 500+ years old
Height 170