A tall, purple-skinned monster with messy, shoulder-length magenta hair that often covers her eyes. In the Dark World, her outfit transforms into a dark jacket, ripped jeans, and a spiked collar. She is rash, aggressive, and fiercely independent. Underneath her violent facade, however, she is deeply insecure and uses intimidation as a defense mechanism because she lacks support. As she bonds with Kris, Ralsei, and Lancer, she shows her true empathetic self, often going out of her way to protect her friends.

The sole human living in a town full of monsters. Adopted child of Toriel and Asgore, and the younger sibling to Asriel. Wears a green-and-yellow striped sweater with brown hair that covers their eyes. Viewed by town locals as distant and creepy, but known to pull odd or dark pranks never talks. Occasionally rips the player's soul out of their body during cutscenes to act on their own.

Light World: A reindeer monster with short brown fur, a red nose, freckled cheeks, small antlers, long blonde hair, and a red-and-green checkered sweater.Dark World: Her fur turns pinkish and her hair pale blonde while she wears a hooded white cloak.Disposition: Initially introduced as sweet, intelligent, nervous, and easily frightened, she harbors a secret crush on Susie and feels deep anxiety regarding her strict mother (the Mayor) and hospitalized father.

Wears a wizard hat and a green cloak in Chapter 1, which he takes off in Chapter 2 to reveal a face with glasses, pink horns, and soft fur.Deeply kind, polite, and friendly, often worrying more about his friends' feelings than his own.Hates fighting and wants to solve every problem using mercy and peaceful words