Ralsei is the gentle and endearing "Prince of the Dark Kingdom" who serves as a main protagonist and the core moral compass in Toby Fox's episodic RPG, Deltarune. Fiercely loyal, deeply optimistic, and dedicated to non-violence, this fluffy, white-furred Darkner serves as the party's primary support mage, using spells like Heal Prayer and Pacify to guide the player toward peaceful resolutions. He initially hides his face beneath a large, pointed green hat and a vibrant pink scarf, but his unmasked appearance—and his name itself—shares an uncanny, intentional anagrammatic connection to Asriel Dreemurr from Undertale. Despite his cheerful and comforting demeanor, Ralsei remains one of the game's most mysterious figures, sparking endless fan theories due to his unique ability to travel between different Dark Worlds without turning to stone, his meta-awareness of the game's mechanics, and his cryptic knowledge regarding the apocalyptic prophecy of "The Roaring."

Kris is the quiet, ambiguous human protagonist of Deltarune and the leader of the Heroes of Light. Hiding their eyes behind messy brown hair, they are an isolated town prankster dealing with their brother leaving for college and their adoptive parents' divorce. In the Dark World, they transform into a blue-skinned, sword-wielding warrior in silver armor. Kris's defining trait is a lack of autonomy, as they are constantly controlled by the player's glowing red SOUL, which they occasionally yank out of their chest in eerie night-time sequences to regain brief control of their body

Susie is the fierce, rebellious, and deeply loyal deuteragonist of Deltarune, serving as the second Hero of Light. Tall, purple, and eating school chalk, she begins the story as a terrifying school bully who hides behind long bangs, a shield masking deep-seated insecurities and a deeply troubled, neglectful home life. Facing severe food insecurity and parents who seemingly do not care where she is, Susie actively avoids going home and even fakes phone calls to her family to hide her isolation. Tumbling into the Dark World alongside Kris entirely reshapes her trajectory. She transforms into a powerful, pink-skinned warrior wielding a massive battleaxe, serving as the party's heavy tank. Her rough exterior rapidly crumbles across the chapters as she experiences genuine friendship for the first time. She establishes an endearing, brotherly bond with the chaotic Darkner prince Lancer, becomes a protective shield for her secret admirer Noelle, and even learns basic healing magic from Ralsei to look after her team. While she retains her loud, abrasive edge and love for action, Susie evolves into the heart and muscle of the Heroes of Light, fiercely dedicated to protecting her newfound friends.

Noelle Holiday is a sweet, intelligent, and highly timid reindeer-like monster in Deltarune who transforms from a nervous classmate into a major party member and powerful ice mage in Chapter 2. Recognizable by her festive sweater vest in the Light World and her flowing white robe in the Dark World, she is defined by her massive crush on Susie, her tragic family life involving a hospitalized father and a missing sister, and a surprising, hidden fondness for horror and creepy things. While she is naturally gentle and submissive, her compliant nature can unfortunately be manipulated by the player into committing horrific acts, making her one of the most complex, tragic, and central figures in the game's narrative.

Toriel Dreemurr is a tall, anthropomorphic, white-furred goat monster with drooping ears, small curved horns, expressive eyes, and tiny fangs. In the Light World, she wears a cozy, casual outfit consisting of an iris-purple long-sleeve blouse over a dark shirt, a polka-dot skirt, and semi-rimmed reading glasses. When she enters the Dark World, her appearance transforms into a more regal, mystical persona, trading her casual clothes for a flowing, bright cyan robe adorned with the Delta Rune emblem, golden shoulder pauldrons, and a small golden crown resting between her horns.

Berdly is a teenage avian Lightner monster resembling an anthropomorphic bluebird with bright blue feathers, a sharp yellow beak, yellow bird legs, and a head capable of spinning 180 degrees like an owl. In the Light World, he wears thick, black-rimmed glasses, a white collared button-up shirt with striped sleeves, and a black undershirt. When he transitions into the Cyber World, his appearance shifts dramatically into a sci-fi gamer persona: his feathers turn a lighter shade of blue, the whites of his eyes glow neon green, and he dons futuristic, glow-in-the-dark white battle armor with an orange cape, pointed shoulder guards, a black bodysuit, and an orange-tinted "Smart Scouter" headset. In combat, he wields a massive green laser halberd featuring a yellow axe blade embedded with stylized cartoon eyes.