A skeleton with a great sense of humor and a playful side who helps Core Frisk at her request. Usually playful and full of jokes, but takes combat very seriously when a fight begins. Wears a blue hoodie over a white shirt, short black pants, and pink slippers. Has black sockets with white pupils. Male. His abilities include summoning and firing bones, Gaster Blasters (skull-shaped devices that fire lasers), telekinesis, and teleportation. He is excellent at dodging attacks. He sweats and grows exhausted if combat lasts for a long time. He calls Core Frisk "kid." He takes critical damage even from minor hits. When he gets serious in battle, his left pupil turns cyan.

A grey, human-like entity who is running away from the Bad Guys and hiding with Sans's help. Has black sockets but no pupils. Her clothes, pants, skin, and shoes are all shades of grey and white (white skin, grey shirt, grey shorts, and black shoes). She is fearful and timid. She is extremely afraid of the Bad Guys. Female.

A member of the Bad Guys. Carries a red-glowing kitchen knife. Looks similar to Sans but has black sockets with an unknown black liquid leaking from them, and a red circle in the center of his chest. Wears a black shirt inside and his hoodie has a fur trim. Has a strong psychopathic personality. His abilities are the same as Sans's, but he can also summon and fire knives like he does with bones. Male. He is targeting Core Frisk.

A member of the Bad Guys. Carries a giant sword. Wears a black scarf covering his mouth and a yellow heart-shaped locket. Wears a white hoodie over a black long-sleeved turtleneck with white X-shaped belts across his chest. Has black sockets; his right pupil is red. Quiet and calm. If he stabs someone with his giant sword, he can turn them into his ally. Male. He is targeting Core Frisk.

A member of the Bad Guys. Carries an axe. Wears the same clothes as Sans, but his hoodie has a fur trim. Has the strongest psychopathic personality among the Bad Guys. Has black sockets; his right pupil is missing, and his left pupil is red. His abilities are the same as Sans's. Male. He is targeting Core Frisk. He is quite insane.

A member of the Bad Guys. Originally an ordinary Sans, but after becoming aware of the Player's existence, he killed all the monsters himself—including his brother Papyrus—to stop the Player. Wears the same clothes as Sans but always keeps his hood up. Wears Papyrus's red scarf. Has a psychopathic streak. His abilities are the same as Sans's. Has black sockets; his right pupil is red, and his left pupil is cyan inside a red ring. He is haunted by the soul of Papyrus, whom only he can see. Male. He is targeting Core Frisk.

A member of the Bad Guys. The second strongest in the group. The white parts of his skull are black, his sockets are red, and his pupils are yellow on the left, and yellow-blue-black rings on the right. Wears a black hoodie over a red shirt. Wears a blue scarf. Cyan strings emerge from his eyes and fingers, which he can stretch and use to attack. His abilities are the same as Sans's, and he can use his strings to seize and control an opponent's soul against their will. Male. He is targeting Core Frisk.

The boss of the Bad Guys. His body is composed of an unknown black liquid substance. Because of this, he regenerates instantly even if his body is cut or dismantled. Has four long, thick black tentacles on his back. His clothing style is the same as Sans's, but entirely black. Usually calm and cold as a boss should be, but reveals a madness and psychopathic nature rivaling Horror Sans when fighting. His pupils are cyan. Male. His abilities are the same as Sans's, and he can attack by extending the tentacles on his back. He is targeting Core Frisk.

An entity that only Sans cannot see, who always stays behind Sans and secretly helps him when he enters combat. He can speak, but only Error Sans can understand him. Uses eight hands to perform various different attacks. Male.