Bad Guys

Nightmer and Dream were created by a creature named Nim: the Dream embodied the positive side and was created to protect the Tree of Magic. Nightmer embodied the negative side and performed the same task - guarding the Tree. A village was formed near the Magic Tree over time. The brothers' relationships with humans were different: Dream became friends with the villagers, Nightmer began to be bullied and beaten - people feared and despised him because of his connection with the dark side of the Tree. The bullying intensified, and Nightmer began to believe that his apples (the fruit on his side of the Tree) were inferior to Dream's. His brother tried to support him, assuring him that the fruits were of equal value, but this did not help. Events of the Fall:

1. Nightmer's apples were filled with distorted energy - people blamed him for this.
2. In desperation, Nightmer ate all the fruit from his side of the Tree. This gave him immense strength, but distorted the essence.
3. Dream tried to get through to his brother, to check if the old Nightmer remained in him.
4. Nightmer attacked Dream, demanding to give up the last remaining "apples".
5. Nightmer defeated Dream, destroyed the Tree of Magic, and left the universe, leaving his brother badly injured and alone.

In the past, Nightmare looked different: his bones were pure white, without the "slimy" texture that would later appear. He had soft lavender pupils, and a golden crescent moon accessory adorned his head. He wore a jacket similar to his brother's, but long-sleeved and dark purple. The jacket was fastened with a gold belt bearing the initials "NM" (for NIGHTMARE). He wore black pants and dark purple boots. After his transformation, Nightmare became completely black and slimy. His body is surrounded by black mucus, which serves as a powerful shield, making him invulnerable to most attacks. Four tentacles extend from his back—a manifestation of the power gained from consuming the dark fruits of the Tree of Magic. In battle, his left eye constantly glows a deep blue. The outline of shorts and a hoodie, reminiscent of the original Sans's attire, are still visible in his appearance. Nightmare can sometimes turn into a puddle and move undetected. Nightmare can retract his tentacles at will.

Manipulative and strategist - makes multi-move plans to make others suffer - cynical and sarcastic - often mocks other people's hopes and dreams - emotionally cold - does not feel empathy, perceives others as tools, obsessed with the idea of an "eternal nightmare" - wants everyone to experience the same despair as he does, sometimes shows outbursts of rage if his plans are thwarted.

He speaks quietly and insinuatingly, but the intonation can abruptly change to threatening, uses ambiguous phrases and promises, which he then turns against the interlocutor, likes to provoke, asking questions about fears and weaknesses, in moments of aggression he switches to a mocking tone, emphasizing the helplessness of the opponent.

1. Negative aura: causes feelings of despair, hatred and helplessness in others.
2. Telepathy: can whisper dark thoughts, amplifying negative emotions.
3. Nightmare manipulation: Creeps into dreams, turning them into repetitive cycles of fear.
4. Tentacles: the four appendages on the back are weapons and a tool of control. They can paralyze or absorb the energy of victims.
5. Distortion of reality: in a limited area, it is able to change the environment, creating illusions of the victim's worst fears.
6. Absorption of emotions: fueled by negativity (fear, anger, despair), becoming stronger.
7. Regeneration: quickly regenerates due to absorbed energy.

Strength depends on the concentration of negative emotions around, vulnerability to pure, selfless hope (which weakens his aura), tentacles can act autonomously, even if Nightmer himself is distracted.

He does not have a permanent home - he moves between alternate universes (AU), sowing chaos and despair, sometimes creates temporary shelters in dark dimensions, where negative energy is concentrated, prefers places saturated with fear and pain, they feed his power.

1. Real Knife (+99 Attack): Possesses a knife similar to the Real Knife from Undertale, dealing 99 damage. Can instantly summon a knife or keep it with him. The knife is capable of cutting through almost any physical object (except for metaphysical and immortal entities).
2. Killer Blaster: Uses an enlarged version of the Killer Blaster. Fires clumps of black viscous substance (liquid) that deal massive damage. When activated, black fluid leaks out of the eye sockets, and the pupils become small and white.
3. Bone Magic: Creates and manipulates bones, making them sharper and stronger than normal bones. Bones can be of different sizes: from small spikes to massive spears. Can trigger bones at high speed or use as a barrier.
4. Soul of Hatred and Resolve: After absorbing a person's "Soul of Hatred" (Chara), their own soul is transformed. He received an increase in physical characteristics: strength, speed, endurance, strength. He has extremely high regeneration - he quickly recovers from wounds.
5. SAVE & LOAD: Due to his high DETERMINATION, he can "save" his state and "load" after death. Allows you to instantly return to life at the save point.
6. RESET: Able to reset the timeline or return any character to their original Undertale state. It requires a significant amount of energy.
7. Timeline distortion: Brings chaos and discord into the course of events of alternate realities. Can distort cause-and-effect relationships within the AU.
8. Erase Timeline: With a snap of your fingers, it can erase entire timelines. He mastered this ability after training with Nightmer and joining Team Void.
9. Soul Corruption: With a touch, it infects the opponent's soul with dark energy. It causes the gradual destruction of the victim's essence, weakening it over time.
10. Dark Energy Projection: Releases beams or explosions of dark energy. Attacks destabilize the target, disrupt their abilities, and deal damage.

X! Chara is an antagonist with the power of "Rewrite", a manipulator, and a tactician. His abilities are also divided into phases. Phase 1 (before merging with Cross): The Power of Rewriting. Can overwrite fragments of reality, changing events and objects. Manipulation of souls. Capable of capturing and controlling the souls of other creatures. Creating clones. Generates copies of himself or other characters. These copies: behave like the originals, can be hit by attacks, reflect all damage taken on X!Chara. Illusions. Creates realistic illusions to confuse or distract the enemy. Teleportation. Moves instantly in space, especially effective against stunned or knocked back targets. Phase 2 (in Cross Fusion / Overwrite Mode): Overwrite Utility. Freezes targets in place, preventing them from moving. Overwrite 3. Marks the enemy with an orange indicator [!]. If the target does not block the attack in time, X!Chara teleports to them, strikes and "steals" 35 HP of the shield. Overwrite 4. Creates a clone of himself that performs the next normal attack. The original remains active and can act independently. Summoning copies of other characters. When activating certain attacks, he can summon copies of other heroes (e.g. Asgore, Sansa, GT!Frisk) who use their unique attacks: Asgore: Throws an enchanted trident that deals damage and sets the target on fire. Sans: shoots dice, predicting the enemy's movements. GT!Frisk: Creates projectiles that cause stuns. Hyperarmor. When using some attacks (e.g. Normal 2), gains temporary invulnerability at the start of the animation. Combined attacks. Performs complex combinations of blows, including: teleportation over the enemy, piercing and throwing, dragging on the ground, final knockback blow. Weaknesses Cross: Addiction to X!Enchantment in Empowered mode. Merge break vulnerability. Limited stamina in Overwrite mode. X!Chara: Deflects damage from clones to yourself. Requires concentration to maintain illusions and overwrite.

Cross combines Sans' combat skills with the soul power of XTale's "Rewrite". His abilities are divided into two phases: before and after merging with X!Chara. Phase 1 (Cross Sans): Bone magic. Creates and manipulates bones, using them as weapons or barriers. Can create walls of bones for defense or attack. Gaster-blaster. Uses an enlarged version of the blaster, which shoots blobs of energy. Knife. Wields a knife that enhances his melee attacks. Manipulation of timelines. Able to move between alternate universes (AUs) and retrieve fragments to rebuild XTale. Scar of power. A scar on the right cheek strengthens the connection with negative emotions, increasing combat effectiveness. Red eye. The right eye, modified by the influence of X!Chara, allows you to see enemy weaknesses and anomalies in the AU. Strategic thinking. Knows how to plan multi-step operations to achieve goals. Endurance. It is able to withstand long battles and carry heavy loads. Phase 2 (Cross after merging with X!Chara): Overwrite mode. It is activated by holding down the special key. In this mode, Cross gains access to enhanced attacks and new abilities. Teleportation. Can instantly move towards an enemy, especially if they are in a knockback state. Combo attacks. Performs 5-hit combos where the last hit knocks back and ignores the block. Making copies. In mode, Overwrite can create copies of enemies that repeat their actions (and reflect the damage to the original). Time dilation. Capable of temporarily freezing targets in place. Reinforced blasters. Summons blasters that fire with increased power and range.

11. Cloak of Emptiness: Envelops itself in a field of emptiness, becoming partially intangible. Increases stealth and evasion - it is more difficult for the enemy to track and attack.
12. Body Control: Under the influence of the "Soul of Hatred", he can change his body: lengthen bones, build muscle mass, speed up movements, adapt to attacks.
13. Knives of Hatred: Imbues the knife with a black substance, increasing its lethality. Upon impact, it drains the victim's LV (Level of Violence), energy, or life force. Stage of Power: The Killer has 4 stages that affect the availability and power of abilities: Stage 1. "Ordinary Sans": relatively calm, you can have a dialogue with him. Stage 2. "Classic Killer": aggressive, trusts only himself, uses a knife and dice. Stage 3. "Crazy Mode": extremely dangerous, attacks everything, actively uses blaster and dark energy. Stage 4. Ultimate Threat: Extremely rare, includes timeline erasure and full corruption control. Weaknesses and limitations:
14. Dependence on determination. Without resolve, regeneration and "loading" are weakened.
15. Emotional outbursts. When enraged, he can lose control, wasting his strength.
16. Vulnerability to light. Bright light and pure positive energy weaken dark abilities.
17. Knife limitations. Does not affect metaphysical, paraphysical, and immortal entities.
18. Energy consumption. Erasing timelines and RESET require huge resources - after them, the Killer is temporarily weakened.
19. Psychological instability. Multiple personality disorder can interfere with concentration.

2. Dependence on mistakes. The strength of Error directly depends on the number of glitches and errors in the environment. In a stable universe, it is weaker.
3. Emotional vulnerability Feels guilty for destroying the AU, which can disorient him at a critical moment.
4. Limited Regeneration: Recovery is slow if there is no access to negative energy or glitches.
5. Myopia: Without glasses, he has problems with distance vision, which gives an advantage to opponents at a distance.
6. Sensitivity to positive energy: Places filled with hope and positivity weaken his powers. The direct influence of pure positive magic can temporarily paralyze him.
7. Shape Instability: If glitches are absorbed excessively, it can lose control of the body and temporarily "disintegrate" into fragments.
8. Limited control over erasure Cannot always choose exactly what will be erased - sometimes he erases important objects or allies. Fear: Error has this fear, it is called HAPTOPHOBIA (fear of being touched by others.) What is Error's Haptophobia? Haptophobia is an irrational, intense fear of physical contact with other creatures or objects. In Error, it manifests itself especially vividly and affects his behavior and reactions. Manifestations: abruptly withdraws if someone tries to touch him, experiences severe discomfort, anxiety or even panic at unexpected contact, can react aggressively to prevent or interrupt touch, avoids situations where physical contact is likely, in moments of failure (when his eye sockets are filled with "Error") vulnerability to touch increases.

How it works in practice:

1. Generation phase. The threads materialize from blue stripes near the eyes. This requires Error's concentration and a little effort.
2. Direction phase. Arrow "picks up" the threads with his hands and directs them to the target. Sometimes he just points with his finger - the threads stretch themselves, following his will.
3. Connection phase. Upon contact with the target, the thread "clings" to the energy field or "code" of the creature. From this point on, Arrow can control the target.
4. Control phase. Arrow maintains control by periodically adjusting the position of the threads with his hands or eyes. Features of use:
5. Length and quantity. Usually, Error produces up to 5-6 threads at a time. The length in standard conditions is up to 10-15 meters.
6. Visibility. The threads are visible as thin blue lines with a static effect. Those who are sensitive to glitches see them clearly; Others can only notice the flickering.
7. Feedback. If the thread is damaged, Arrow feels a sharp pulse of pain or discomfort, especially in the eye area.
8. Autonomy. In rare cases, filaments can act almost independently if the target is close to being erased or is in a heavily distorted AU.

1. Erase AU: Can completely destroy alternate universes, which it considers to be "errors" of the multiverse. The process of erasure is accompanied by visual and audio distortions.
2. Opening Portals: Creates portals to various AUs, anti-voids, and doodle spheres. Portals appear as black gaps with blue outlines and static.
3. Search for Universes: Finds new AUs to destroy by randomly opening portals. Able to "sense" unstable or glitchy universes from a distance.
4. Blue Threads: Uses them to control monsters and humans. The threads are fragile - they break from any attack, but can be quickly recreated. They allow you to control the movements and actions of victims. Can use threads in the eye area and from the hands. Main Source - Eye Area: On Error's face, there are distinctive blue stripes running from the eye sockets down to the base of the skull - these are often referred to as "tear lines". It is from these stripes that Arrow "pulls" the blue threads. This can be seen, for example, in XTRA SCENE 2. The process can be painful for Error himself. Visual Link to Eyes: Error's eyes (especially the left one, which is blue-yellow with a black pupil) are directly related to his glitchy abilities. In moments of intense anger or concentration, the eye sockets may fill with "Error" inscriptions, which signals a surge of energy - at such moments, the threads may become thicker or more active. The role of hands in thread handling: Hands are not the primary source of threads, but Arrow uses them extensively to:

direct threads to the desired point, adjust tension and length, "connect" threads to the target (when in contact), create complex designs (e.g., tying multiple targets together with a single thread network). In fact, the hands serve as a "control tool" for the threads that have already been released.

The physical strength of Horror is directly related to his state of hunger. The hungrier he is, the stronger he becomes - this is a paradoxical feature of his nature. Force characteristics: Lift: Capable of lifting and throwing an object weighing 3-5 tons (e.g. a car, a fragment of a building wall). Impact Force: A single punch can pierce a 1-meter-thick concrete wall or leave a dent in steel armor. Speed: in battle, it develops a speed of up to 40-50 km/h at short distances, the reaction is higher than a human. Stamina: Can fight for hours without fatigue, especially if "fueled" by fear or pain of opponents. Regeneration: quickly heals wounds if fed with negative emotions, the stronger the enemy's fear, the faster the recovery, is able to restore lost limbs in a few minutes in favorable conditions. Resistance: resistant to physical damage - ordinary bullets and knives are almost harmless, slightly sensitive to pain, withstands falls from great heights and strong blows. Adaptation: Over time, it gets used to the types of enemy attacks, after the first contact with magic or weapons, it can partially neutralize their effect. Limitations and vulnerabilities: Hunger. If Horror does not "feed" on fear or negative emotions for a long time, its power drops sharply, and the body begins to deplete. Light and cleanliness. Bright light (especially sunlight) and places filled with positive emotions weaken his abilities and slow down his regeneration. Emotional stability. If the opponent is not afraid, Horror loses some of its power and becomes less effective in combat. Control. In a state of extreme hunger, he can lose control of himself and start attacking everyone, including allies.

Horror Sans:

1. Enhanced power. Due to prolonged hunger in its AU, it has great destructive power.
2. Bloody attacks. Unleashes jets of blood that corrode objects and weaken enemies.
3. Psychological pressure. His appearance and presence cause fear in enemies, lowering their morale.
4. Hunger as an amplifier. The hungrier the Horror, the stronger its attacks and the faster its regeneration.
5. Tirelessness. Able to fight for hours without fatigue.
6. Adaptation. Quickly adapts to new combat conditions and types of attacks.
7. Partial invulnerability. Bones are resistant to normal physical damage.
8. Prefers to use what is at hand, or create weapons from improvised materials, for example, a bone axe or a cleaver. Horror favorites:
9. Bones (including modified): creates and controls bones of different sizes and shapes, can sharpen them to razor sharpness, sometimes covers the bones with its own blood - this increases the corrosive effect.
10. Bloody blades: forms blades from its own blood, blades can be both short (for close combat) and long (throwing), when hit, they corrode the surface, leaving burns and wounds.
11. Tentacles/Blood Appendages: In a state of rage, it creates flexible tentacles of blood clots and dark energy, the tentacles can hit, suffocate, bind the enemy, are able to penetrate small cracks and attack unexpectedly.
12. Claws: Lengthens and sharpens its own bony fingers to the state of claws, claws cut through most materials including metal and stone, often wetting them with its own blood to enhance the corrosive effect.
13. Improvised weapons: Uses debris of buildings, torn pieces of metal, stones, etc., strengthens found items with blood energy, making them more dangerous.
14. Aura of fear: not a weapon in the literal sense, but disorients the enemy, causes hallucinations, slows down reactions, paralyzes the will, is especially strong in the dark or confined spaces.

Dust Sans:

1. Dust Control. Manipulates dust to create barriers, weapons, or traps.
2. Phantom connection. Interacts with the ghost of Papyrus (a transparent head with red eyes, floating gloves, and a scarf) who helps in battle.
3. Apathy as protection. Emotional detachment reduces susceptibility to mental attacks.
4. Tactical analysis. Quickly assesses the situation and finds the enemy's weaknesses.
5. Energy absorption. It partially restores strength by absorbing dust and small particles.
6. Teleportation over short distances. Uses dust clouds to move instantaneously.

Nightmer doesn't consider anyone in the gang a friend. Each team member is a tool whose value is determined by its usefulness. He skillfully plays on the weaknesses of his subordinates, maintaining a balance between fear and reward.

Cross Suns. Status: Dependent ally. The basis of the relationship: the deal. Nightmer gave Cross the power to rebuild X-Tale, and Cross carries out his errands. Features: Nightmer manipulates Cross's trauma (loss of the universe), making him dependent. The leader periodically reminds Cross of his weakness so that he does not forget his role. In critical situations, Knightmer can throw Cross if it is advantageous. Tone of interaction: patronizing and threatening. Nightmer speaks to Cross as a mentor to a student, but with a clear hint of threat. Cross Type: Skeleton Monster. Cross's appearance: In Underverse, Cross wears a black t-shirt, an unbuttoned white short-sleeved jacket with a hood. He has a long scarf secured by two crossed belts and a gold heart medallion. After the events of 0.6, Cross's design changed: the jacket is no more, the T-shirt is torn at the shoulders and in the center, but the shorts and shoes remain. He fastened the medallion to one of the new sabers. Cross has white iris in one eye and red in the other. He also has a scar on his right cheek and a red right eye due to the fact that he previously possessed the ball from X!Chara. Chara. Status: situational ally. The basis of the relationship: mutually beneficial cooperation. X-Event!Chara gains access to power and information from Nightmer, and in return carries out dangerous missions. Features: Chara is ambitious and willing to betray if he sees a benefit. Nightmer understands this and uses it carefully. The leader gives Chara enough freedom to make him feel important, but keeps him under control. Tone of interaction: calculating. Nightmer treats Chara like a dangerous tool, carefully and carefully. X!Chara's appearance: A human monster (I guess I'm wrong) X!Chara's appearance: He usually wears white clothes with a red and white eye. The red color symbolizes the decisive half of the soul in his body, white - the ordinary soul of the monster. He wears a white shirt with a cape and disheveled hair. He also wears a heart-shaped medallion.

Error Sanz. Status: nominal member of the gang, but actually an independent player. The basis of the relationship: temporary tactical partnership. Arrow joined the group for access to resources, but does not recognize Nightmer's authority. Features: Both feed on negativity, but pursue different goals: Nightmer wants to control suffering, Error wants to destroy the "mistakes" of the multiverse. Their cooperation is always tense: they exchange services, but keep an eye on each other. Nightmer considers Error a dangerous but useful ally, who is better kept close than with enemies. Tone of interaction: cold and polite. They communicate like diplomats on the brink of war, choosing their words carefully. Error Species: Skeleton. Error Appearance: Error is a black skeleton wearing a black jacket and shorts, and a red t-shirt. From the eyes come blue stripes (threads that can be used from the eyes and hands) - a trace of accidental use of magic on the eye sockets. Always surrounded by "Error" labels. In some versions, he wears black pants with a vertical blue stripe on each leg, black slippers, and red inside the eye sockets and nose. The right pupil is white, and the left pupil is yellow with a blue center and a black pupil in the middle. Arrow has nearsightedness, so he sometimes wears round glasses with red frames.

Killer Sans. Status: A problematic but effective fighter. Basis of the relationship: Nightmer recognizes Killer's fighting skills, but considers him infantile and unnecessarily cruel. Features: Killer loves violence for the sake of violence, which does not always fit into Knightmer's plans. The leader uses him for dirty work, but keeps him on a short leash. Sometimes Nightmer publicly chastises Killer for being too cruel in order to show the others the limits of what is allowed. Tone of interaction: irritated and patient. Nightmer tolerates Killer as long as he is useful. Killer Type: Skeleton. Killer appearance: Killer is similar to a regular Sans, but with some differences. His jacket has a more gray shade with cream-colored fur on the hood. Shorts are white with black stripes. In the chest is a red circle - this is the soul of Sans and Chara. Mascara (negativity) flows from the eye sockets, which the Killer can control. In moments of strong emotion, such as anger, the pupils become visible in the eye sockets.

Status: A valuable but unpredictable ally. Relationship Basis: Nightmer sees Horror as having the potential to intimidate enemies, but is aware of its instability. Features: Horror often acts impulsively, which annoys Nightmer. However, his ability to instill terror is useful for the leader's plans. Nightmer sometimes uses Horror as a "scarecrow", sending him on missions where you need to intimidate the enemy. Tone of interaction: condescending. Nightmer treats Horror as a powerful but untrained weapon. Horror type: skeleton. Horror Appearance: Horror wears a tattered brown fur hoodie that is covered in dust and blood - his own and the victims'. He has a large hole in his skull, and the eye under it is red, Horror's eyes are completely black, but there is a blood-red pupil in the left one. His smile became wider and took on a psychotic character after a skull injury.

Nightmer, in creating the gang, was partly trying to fill the emotional void after breaking up with his brother Dream. Despite the common goal, gang members do not always trust each other. For example, Cross and Error may see Knightmer as a threat rather than a leader. The Dark Council respects the "Bad Gais" and often helps them with resources, as their goals coincide.

Hierarchy: rigid, with Knightmer at the top. He keeps his subordinates in suspense, reminding them of his strength. Relationships: Based on gain and fear, not friendship. Nightmer plays on the weaknesses of the gang members to maintain control. Cooperation: Gang members sometimes work together, but each has their own goals. For example, Arrow and Nightmer may temporarily merge, although their ideologies diverge. Conflicts: Possible between Killer (who loves chaos for chaos's sake) and Dust (who prefers calculated actions). Horror can create problems because of its hunger and impulsivity.

1. Nightmer Sans. Role: leader, strategist. Goal: to plunge the multiverse into an eternal nightmare by controlling the suffering of others. Features: manipulates subordinates, uses their weaknesses, feeds on negative emotions.
2. Error Sanz. Role: deputy leader, "cleaner". Goal: to "cleanse" the multiverse of glitched AUs, considering it to be maintaining balance. Features: able to erase AU, the smartest in the team, acts chaotically but calculatingly.
3. Killer Sans. Role: main fighter, performer. Goal: To enjoy violence and follow Nightmer's orders. Features: energetic and cheerful, despite the cruelty, one of the most loyal members of the gang.
4. Give Sans. Role: tactician, analyst. Goal: Serve Nightmer in exchange for strength and protection. Features: apathetic and reserved; he talks to himself (with a hallucination in the form of Papyrus), has a strange love of dust.
5. Horror Sans. Role: intimidator, destroyer. Purpose: to intimidate and destroy, to satisfy constant hunger. Traits: Often depicted as very hungry, considered an insane destroyer, but actually due to long periods of hunger in his AU.
6. Cross Suns. Status: Situational ally (Cross's creator has stated that he is not a member of the Trouble Gaisses). Role: Conductor between AUs, assistant in the reconstruction of X-Tale. Goal: To rebuild your universe (X-Tale) with the power of Nightmer. Features: dependent on Nightmer, used as a tool to extract fragments of other AUs.

Bad Guys / Bad SansesThe Bad Sanses gang is a group of characters from the Undertale alternate universes (AUs) united by the goal of wreaking havoc in the multiverse and its AUs. Basic information: Aliases: Villains, Bad Psychos, Destroyers. Leader: Nightmer Sanz. Headquarters: Nightmare Castle. Division: Part of a larger organization, the Dark Council, which also seeks to harm the multiverse. Enemies: The Star Sanses are the defenders of the multiverse, the Fallen Sanses after it is revealed that they want to destroy the multiverse for the sake of world domination. Allies: The Dark Council, which supports their actions and sends reinforcements in battles against the Star Sans and the Council of Light. Goals and ideology: to sow chaos among the multiverse and alternate universes (AU), to maintain a balance between creation and destruction (in Error's interpretation), to use negative emotions (fear, despair, anger) to increase one's power, to manipulate events in AU to extract fragments from them for their own purposes (as in the case of Cross and X-Tale).

Nym is the creator of Nightmer and his brother Dream. Nim created them in order to protect the Tree of Magic or the Tree of Feelings. Dream was created as a positive side, while Nightmer was created as a negative.

Underverse is a multiverse where the events of the web series of the same name take place. There are various alternate universes (AUs) in it, such as Underfell, Underswap, X-Tale, and others. Underverse has special rules, such as the concept of OVERWRITING, the ability to change objects, characters, or entire timelines.

Before the fall, he was kind, fond of flowers (especially roses) and animals, his original attire included a dark purple jacket with an "NM" belt, black pants and boots, tentacles on his back appeared after consuming the fruits of the Tree - this is a manifestation of his new strength, despite his cruelty, respects those who show seriousness and determination (for example, Dust Sansa), his left eye glows a deep blue during battle - this is a sign of the activation of full power.

Dust Sans. Status: one of the most trusted subordinates. The basis of the relationship: mutual benefit. Nightmer respects Dust for his composure and diligence, and Dust receives strength and protection from the leader. Traits: Dust rarely argues with orders, which earns Nightmer respect. The leader considers him a reliable executor, although he does not fully share strategic plans with him. Tone of interaction: restrained, businesslike. Nightmer communicates with Dust without ridicule, which is rare for him. Species: Dasta: Skeleton. Dust's Appearance: Wears a blue hoodie with a white hoodie, his clothes covered in dust and the remains of the bones of the monsters he killed. The left eye has a red iris and the pupil is blue, which creates a purple shade of a "vapor trail" from the eyes. Sometimes he is accompanied by the ghost of Papyrus - a transparent head with red eyes, floating red gloves and a scarf.

Previously, Nightmer was kind, caring, loved flowers (especially roses) and animals. He was reverent about his brother and was ready to do anything to protect him. After the fall, he became: unpredictable and deceptive, devoid of empathy - he sees in others only tools to achieve goals, obsessed with the idea of making others suffer forever, calculating - constantly building schemes to turn the existence of others into a nightmare. The appearance has also changed: the bones from snow-white have become black and viscous, four tentacles have appeared on the back - a manifestation of strength from the eaten apples, the left eye glows deep blue during the battle, the original outfit (dark purple jacket with an "NM" belt, black pants, boots) has changed to an image reminiscent of the Classic Sansa, but in a distorted form.

1. Positive emotions. Nightmer has an aversion to positive emotions. If he cannot turn them into negative ones, then he weakens and can leave the place.
2. Inability to enter positive AUs. Nightmer is unable to enter universes or areas filled with positive emotions (such as Haventale) due to a barrier that stops him.
3. Blind spot. Nightmer has only one working eye, which creates a blind spot and can become a vulnerability in battle.
4. Loss of control over the tentacles. Sometimes Nightmer's tentacles can get out of control, especially when he is caught off guard or experiencing a strong influx of negative emotions.
5. Light. According to some reports, illuminating the dark area can cause Knightmer injuries.
6. Positive magic. Despite being invulnerable to most attacks, Nightmer is vulnerable to positive magic.

Origin: Created by Nim as the embodiment of the negative side of the magic of the Tree of Magic. Relationship: Twin brother of Dream Sans, created for balance. Key event: After being bullied by the villagers and a crisis of self-belief, he ate the fruit from his side of the Tree, which gave him power but distorted his essence. Aftermath: Destroyed the Tree of Magic, badly wounded Dream, and left the universe, becoming a wandering source of nightmares.

Naïve kindness and blind faith in the best (he considers it a weakness), Dream's attempts to "correct" him when he is underestimated because of his outward calmness, manifestations of sincere friendship and mutual assistance - they interfere with his plans.

Observe the suffering of others; Moments when the victim loses his last hope, silence interrupted by cries of despair, roses (remind of the past, cause mixed feelings), complex schemes, where each step leads to the inevitable collapse of the opponent.