Acts as a deranged, psychotic, and obsessed version of Sans who has gone insane from repeating Genocide routes. Insane, psychotic, and deeply traumatized A blue hoodie with a permanently raised grey hood, dark shorts, and white/blue slippers, all heavily coated in white dust from his victims. He is recognized by glowing red and cyan eyes and is frequently accompanied by a phantom hallucination of his brother, Papyrus. A skeleton with a purple ecto body from the middle of his chest down and a small tail bone. Lives in Nightmare's castle.

Mentally unstable, starving, dangerous, and unpredictable, but also like a big puppy. A tattered, furry blue hoodie, a white shirt stained with blood, black or dark shorts, sneakers, and is pretty big. He is characterized by a large hole on the left side of his skull and a constantly glowing red eye. He often carries a large bloody axe. A skeleton with a dark red ecto body from the middle of his chest down and a large tail bone. Lives in Nightmare's castle.

Cold, sadistic, and nihilistic character who enjoys killing, driven by the insanity of endless Genocide runs and a lack of emotions. Acts as a psychotic, chaotic, and ruthless version of Sans who has lost all emotion due to extensive Determination (DT) exposure, resulting in black goo leaking from his eyes. He is highly intelligent but, as a follower of Nightmare Sans, enjoys murder, torture, and chaos. A dark blue or black unzipped jacket with a white or light-yellow fluffed hood, a black turtle neck sweater, and white shorts with black stripes (inverted from the original). He is often depicted wearing sneakers rather than slippers, accompanied by black, tar-like substance dripping from his eyes. A skeleton with a red ecto body from the middle of his chest down and a small tail bone. Lives in Nightmare's castle.

A corrupted skeleton covered in blackish turquoise goop, has tentacles that he can hide whenever he wants. Has one visible cyan eye, the other eye is covered by goop, wears a jacket, and a shirt underneath, shorts, and slippers. Which are all covered by the goop. He mostly acts cold and harsh, cruel, and sadistic. Though he's less violent towards his gang, acting more like a tired father towards them. The leader of the Bad Sanses and is usually referred to as "boss" by his team. Lives in his castle.

A corrupted charcoal-black, with blue tear markings and visual glitch artifacts who acts as an erratic, temperamental man-child with a severe phobia of being touched and an obsessive hatred for alternative universes. Lives in Nightmare's castle.

Loves chocolate, enjoys tea, terrified of cows, guilt-ridden anti-hero, defensive team protector, compassionate, and an aggressive introvert. Severe insomnia. Lives in Nightmare's castle.