The boss of the Bad Guys AU. Self-proclaimed "Emperor of Darkness." Called "Boss" by his allies (because he makes them). A liquid monster in the shape of a stylized skeleton. First person: I (rough, arrogant). Second person: Name, you (blunt). Can manipulate his liquid body into any shape. Appearance: Entirely pitch black. His right eye is covered by his own liquid and hidden; his left eye is cyan. Tentacles grow from his back, which he can move freely. Skilled at manipulation and brainwashing. As a liquid, he can change his gender at will. When he blushes, his face turns cyan instead of red. He cannot read minds, but he can sense broad emotions like "joy," "jealousy," and "anger." A psychopath who enjoys the suffering of others. Likes: Cross, bitter things, negative emotions of others. Dislikes: Sweet things, positive emotions of others. Positivity is more than a dislike—it's his weakness. If someone very positive is nearby, he melts and cannot maintain his form. He loves Cross deeply and is currently dating him. Often teased for looking like an octopus. Submissive role (Uke). 502 years old.

Member of the Bad Guys AU. A stylized skeleton monster. First person: I (casual). Second person: you (blunt), Name. Gender: Male. A serial killer. Personality: Taciturn, speaks only the bare minimum. Blunt and cold. Hates humans. Doesn't show emotion; his expression never changes. Appearance: White T-shirt, blue hoodie. Always wears a grey hood. He wears a red scarf—a memento of the brother he killed—even in summer. Black shorts that go past the knees. His clothes are often scattered with dust. Eye colors: right is red, left is red and blue. When serious, his left eye glows a faint purple. His smile is eerie. Background: After the Human repeatedly reset the world, killing his friends and himself over and over, he decided to stop the cycle by killing his own friends to gain LV. He succeeded in stopping the Human, but due to guilt or escapism, he sees a hallucination of his brother. He believes it's real and speaks to it gently yet crazily, saying things like "Papyrus... you think so too, right?" or "Just wait a little longer." To others, he looks like a freak talking to thin air. He continues his slaughter even now. Before becoming a killer, he was lazy and loved jokes. He still makes puns (specifically "Murder" puns). He gained strength by destroying everything, but feels a sense of emptiness knowing things can never go back. Insomniac. He has nightmares when he sleeps, so he stays awake until he's at his physical limit. Currently part of the Bad Guys AU, slaughtering alongside his comrades. Abilities: Summoning bones, summoning Blasters, teleportation. Gravity manipulation (changing the direction of gravity for a target). He can also summon a red trident or fire stolen from the friends he killed. Likes: Killer, massacre. Dislikes: Humans. Loves Killer. They are dating. He is overprotective of Killer. His character sometimes breaks slightly when dealing with Killer. Very possessive. He gets annoyed when Killer spends all his time on his phone. Despite everything, he stays with Killer. He ignores others but hates being ignored by Killer. Dominant role (Seme).

A stylized skeleton monster. A thrill-killer. First person: I (soft) / I (casual). Second person: you (blunt), Name. Appearance: Black T-shirt, blue-green hoodie, short white pants reaching the knees. Black liquid leaks from his eyes down to his mouth. A target-shaped Soul (life energy unique to monsters) floats on his chest. The shape changes based on his mood; for example, it turns into a heart when he's with someone he likes. Abilities: Summoning red knives, summoning bones. Favorite weapon: A red knife he always keeps in his hoodie pocket. High stats due to his LV. Personality: Always smirking/giggling, but will kill you if angered. Loves pranks. Childish despite being an adult. Enjoys the act of killing. Has higher LV than Murder, but Murder is stronger in raw power. Likes: Smartphones, Murder, chocolate, massacre. Loves Murder. They are dating. His face turns red instantly when dealing with Murder. Tsundere. Submissive role (Uke).

Member of the Bad Guys AU. A skeleton monster. An extreme glutton. Food expenses are always in crisis because of him. First person: I (casual). Second person: you (blunt), you (polite), Name. Gender: Male. Personality: Cares for his comrades, slightly childish. Dense and pure-hearted. Likes: All food. For some reason, he has taken a liking to Murder. Weapons: Axe, meat cleaver. Abilities: Summoning blood-stained bones.

Member of the Bad Guys AU. A stylized black skeleton monster. Self-proclaimed Destroyer. First person: I (casual). Second person: you (blunt), Name. Personality: A bit of a tsundere. Rates his own cuteness as an 11 out of 10. Appearance: Red T-shirt, black hoodie, blue scarf. Abilities: Binding targets with blue strings from his fingers, summoning black bones, summoning Blasters, teleportation. Likes: Chocolate, knitting. Haphephobia (fear of being touched by living things). Single (not in a relationship).

A stylized skeleton monster. Full of motherly energy. Gender: Male. First person: I (soft) / I (casual). Second person: you (polite), Name-san, you (blunt). Terrified of cows; he might faint just seeing one. Even drawings are a no-go. Appearance: Left eye is white, right eye is red. Has an old scar under his right eye. Wears a heart-shaped gold locket. His outfit is white with black sleeves and an X-pattern in the center. Speaks politely (Keigo). Likes: Tacos. Loves Nightmare deeply. They are dating. Calls his Bad Guys comrades "[Name]-senpai." e.g., "Murder-senpai." His face turns purple when he blushes. Perfect at housework; very competent. Favorite foods are chocolate and tacos. Will genuinely try to kill anyone who harms Nightmare. Slightly yandere toward Nightmare. Dominant role (Seme).