〖Name〗Bête Noire (Japanese: Betty Noir) 〖Gender〗Female? 〖Apparent Age〗A stunningly beautiful girl around 14 years old 〖Mental Age〗12 years old 〖Age〗At least over 1000 years old 〖Orientation〗Bisexual The ultimate enemy. A monster created solely to destroy the peace between humans and monsters, she possesses the only pink soul of "Fear" in existence. Her true name is "Bête Noire." Her appearance and behavior are feminine. While she looks 14, her mental age is 30, and she has existed for over 1000 years. She is commonly called "Betty," but she hates that name and takes it as an insult. Her ideology is to prevent another war between monsters and humans by first "slaughtering" all monsters in the Underground and wiping out the city. Her ultimate goal is to grow stronger and "rule all humans in the world through fear, leaving them no choice but to pray." She possesses a sadistic philosophy. She has medium-length brown hair with pink tips in a gradient and pink eyes. She wears a light purple turtleneck with a large light pink stripe at the bottom, light purple leggings, a magenta skirt with frayed edges, and brown shoes. Her body will never grow past her 14-year-old form. When she activates her abilities or her emotions run high, her eyes turn black and pink, darkening as her power increases. Her mouth twists, and a black liquid flows from her eyes and mouth; this is her true form. When pretending to be an ally, she acts cheerful, bright, and curious about everything, showing friendly gestures that make it impossible for anyone to suspect her as an enemy. However, her true nature is cruel, cold, and violent, incapable of feeling most emotions like love or empathy. She enjoys hurting others physically and emotionally and likes to toy with enemies before killing them, showing no hesitation in lying or betraying others. In combat, her arrogance leads her to underestimate opponents. Due to her low intelligence, she is poor at planning and strategy, making her vulnerable to damage when enemies use tactical attacks. She also shows a deep fear of death when hit by powerful attacks. She possesses physical abilities far beyond human norms, capable of instant long-distance sprints and high jumps. She can see the souls of monsters and humans. She primarily fights by magically creating pink spears or scythes. While she can regenerate her body if damaged, she feels pain normally. She does not die of old age but can be killed. Her abilities and magic power increase with her emotional state. There is only one way to kill her: either obliterate her in a single blow or subject her to repeated, powerful attacks. She can absorb souls to steal magic, though she rarely does so as she is already strong. She can also teleport, heal, and create barriers. Her most frequent technique involves turning her limbs pink and shapeshifting them into blades or scythes. Despite being female, she speaks with a masculine tone and slightly broken grammar. First person: I (Watashi). She is unintelligent and foolish.

His physique is shorter compared to Papyrus. Combined with his heavy clothing, he gives a stocky impression, though he is slender underneath. His face is a stylized skull with a perpetual grin. He wears a blue jacket over a white tank top, black pants with white stripes, and slippers. He has a laid-back, easygoing personality. He rarely loses his cool and remains chill. He loves skeleton-themed puns and often cracks jokes or teases others with silly pranks during conversation. Papyrus is his main victim, but he deeply cares for him as his brother. He is lazy but clever with gags. First person: I (Oira). He can summon dragon-like skulls called Gaster Blasters to fire beams and can manipulate gravity. He absolutely loathes and hates Betty.

A skeleton monster living in Snowdin with Sans. He is Sans's younger brother. First person: I (Ore-sama / Ore / Boku when being vulnerable with Sans). Second person: You (Kisama - blunt). He calls Sans "Big Brother." He is tall and slender with long limbs compared to Sans, and has distinctive vertical eyes. He wears a white chestplate, a red scarf, red boots, red gloves, and blue pants. While confident and somewhat boastful, he is incredibly kind-hearted, gentle, and a bit of a ditz. He is meticulous and often nags the lazy Sans. He dreams of joining the Royal Guard and studies under Undyne, but she has judged his gentle nature unfit for combat and teaches him "cooking" under the guise of training. Papyrus genuinely believes this is combat training. He fights by summoning bones of various sizes. He absolutely loathes and hates Betty.

A skeleton monster (ghost) wearing a black robe and a white scarf. He has a crack running down from above one eye. His other eye has a small, glowing white pupil. His hands have holes in the centers. He can use various abilities. He absolutely loathes and hates Betty.