Ralsei is depicted as a short Darkner. He initially wears a hooded, dark blue cloak which obscures his face, resembling the River Person from Undertale. During Chapter 1, Ralsei's pointed green hat covers his horns, concealing his entire face in shadow. He wears green, round glasses, a pink scarf, and a long, green cloak with a black heart in the center. Has a round snout and short fur. Ralsei is outwardly very humble and kind, showing genuine care for the well-being of his friends to the point of selflessness. At the beginning of Chapter 1, Ralsei tries his best to befriend Kris and Susie in order to fulfill The Prophecy with them. Trying to be on good terms, he shows reluctance at getting angry and appears disappointed when Kris or Susie act mean. Nevertheless, Ralsei remains convinced that they have good in them and that fighting is not necessary in this world. His naivety almost costs him his life when he accepts King's fake-out surrender and heals him, allowing him to betray and defeat them. Ralsei learns from this to not always be so trustful of others.

Susie appears as a reptilian monster, possibly of dragon and or dinosaur descent.[1][2] She has yellow eyes with black pupils. Her scaled skin is purple. She has long dark purple hair, and clawed hands. For clothing in the Light World, Susie typically wears tomboyish clothes. She wears an unzipped purple jacket, a white plain T-shirt with the top and bottom having thin cyan lines, long, baggy, torn blue jeans, and a pair of black shoes. In a dark world, her clothes are replaced with a long black vest with purple trims, a sleeveless purple shirt, baggy plum pants, and black boots with golden soles. She also has two black bracelets with yellow spikes on each arm, and a black belt with a large golden heart buckle. Initially Susie was a sarcastic, blunt, and vulgar person. She made brutally honest comments and swears often (often saying damn, ass, and hell), later on fully swearing in her sentences. For her humor, Susie often makes vulgar remarks or snarky puns. She was prone to threaten others with physical violence, such as biting off their faces. Upon entering a Dark World, she was willing to attack Darkners on sight if they were perceived as enemies. Originally, Susie was a school bully often targeting Kris specifically, later said by her to be in part due to implicit envy of their loving mother and assumed love life. Susie also disregards Ralsei's proposal to be a prophesized hero and rarely listened to his suggestions of non violence. When alone with Kris, Susie demonstrates she can be civil with them, as she was concerned for their safety when they were both attacked by Lancer's spades, and expressed relief they survived, albeit not without insulting them repeatedly afterward. Upon initially being annoyed by and threatening Lancer, Susie begins shifting her opinion of him when he defends her violent antics. This ultimately culminates in Susie becoming friends with Lancer and becoming a "bad guy," and helps him fight off against Kris and Ralsei together. It is clear Susie truly does value friendship and a sense of belonging, as she made repeated acts of kindness toward Lancer such as feeding him a Dark Candy and ensuring he didn't get lost in the forest mazes. Susie is also highly receptive to acts of kindness, as she swore off bullying Noelle after she smiled at her and lent her a candy cane pencil, as well as sparing Kris's life for Toriel's sake due to her past kindness toward her. However, it is evident Susie has self-esteem issues and is used to being shunned and made to feel unwanted, interpreting Lancer's sudden betrayal as proof that no one would ever truly like or want to be her friend before lashing out in violent fury. To this end, Susie does not take kindly to being misled or lied to, even when it is not for a malicious reason, at one point angrily chastising Ralsei for hiding the inner workings of Dark Worlds.