Characters of Undertale and Deltarune

A screenshot from the 'True Pacifist' ending of Undertale, featuring friends the player makes along the way. From left to right: Toriel, Sans, Papyrus, Frisk, Undyne, Alphys, and Asgore.

The fantasy role-playing video game Undertale, developed by Toby Fox, takes place in a universe where monsters once coexisted with humans, but have long since been forgotten in modern times. Its main character is a human child who falls into the Underground, a large cave below Mount Ebott where human wizards trapped the monsters following an ancient war and from which they seek to escape. Its spiritual sequel, Deltarune, is an anagram of Undertale, and takes place in a parallel universe featuring many of the same characters. In Deltarune's universe, humans and monsters still coexist in the modern day. The main character, Kris, discovers the Dark World, an alternate realm inhabited by Darkners, which are beings brought to life from objects originally from the Light World (the regular world). They embark on a quest to close the Dark Fountains before darkness overtakes the real world.

The following is a list of major characters who appear in one or both games in the series. The characters of both games were well received by critics and fans for their humor and in-depth characterization shown through different moral choices. Some characters gained notoriety for their ability to break the fourth wall, manipulating gameplay elements normally only accessible to the player, such as saving.

Undertale and Deltarune

Toriel and Asgore Dreemurr

Main articles: Toriel and Asgore

The Queen and King of the Underground in Undertale, who are members of a powerful, goat-like species called Boss Monsters. Asgore rules over the monster city of New Home. Toriel split from Asgore due to his desire to kill humans to collect their souls and free the monsters using force following the deaths of their children Asriel and Chara, and now lives alone in the Ruins.

Toriel initially attempts to adopt the protagonist as her child; when they try to escape, she acts as the game's first major boss, attempting to prevent the player from entering the Underground and falling prey to Asgore. It is not made immediately obvious that she can be spared, making her accidental death a common occurrence. The tendency of players to reload in an attempt to save her is one of the game's first demonstrations of Flowey's "meta" knowledge, as he will remember if the player has previously killed Toriel. In the Toriel Ending, Toriel reclaims her position as Queen of the Underground and makes a rule that humans will be treated as friends. This ending can play out in two different ways, with her either remaining in power or abdicating following Undyne leading a revolution if she was spared, or returning to the Ruins, where she Sans, and Papyrus if he is spared, will accompany her.

Toriel has received attention from critics for her personality and the atypical moral choice of her boss battle. Nathan Grayson of Kotaku stated that while he killed Toriel during his playthrough, his encounter with her made him cry due to her friendliness and relatability as a character. He also praised the game for remembering this on his next playthrough. Julie Muncy of Kill Screen criticized the encounter with Toriel as unintuitive, saying that she lost the ability to trust the game after seemingly having to kill her, which forced her onto the game's "Neutral" route. Jess Joho, also of Kill Screen, called the character "relying on the inhumanly selfless portrait of motherhood", but doing so with a purpose, praising the boss encounter with her as respecting the player's ability to think through a problem, as well as their basic instincts as a human being. She stated that the game holds up a mirror to "patriarchal" game design that encourages players to impatiently "sacrifice their own mother and humanity" rather than engaging with the enemy on a "human level".

Asgore is encountered late in the game and serves as the penultimate boss. Despite having a fearsome reputation in battle, he is actually a kind father figure, and is reluctant to go through with his plan to destroy humanity and feels regret for killing the six humans that arrived before the player. Flowey kills him if the player attempts to show him mercy, but survives in the game's True Pacifist Route after Toriel intervenes.

In Deltarune, Toriel and Asgore are Kris' foster parents. Toriel is a teacher at a local school, while Asgore is divorced/separated from her and runs a flower shop called 'Flower King', referencing his Undertale incarnation's gardening hobby and being the King of the Underground. Asgore was previously the chief of police before being fired following an unknown incident.

Asriel Dreemurr

Main article: Flowey

In Undertale, Asriel is the now-deceased prince of the Underground, who Chara, his adoptive human sibling, convinced to participate in a plot to collect six human souls from the surface. After absorbing Chara's soul and leaving the Underground, Asriel refused to fight back against the humans who mistook him for Chara's killer and killed them both. Asriel was then reincarnated as Flowey, but without his empathy and compassion. In the game's True Pacifist Route, Flowey transforms into an adult representation of Asriel, known as the "God of Hyperdeath". After being defeated, Flowey returns to the form of child Asriel and regains his empathy, albeit only temporarily.

Jason Schreier of Kotaku called Asriel's final boss fight one of the greatest in video game history, citing its climactic music and the necessity to save your friends from him. Describing the sequence as "spectacular" and noting the emotion of the fight, he stated that, "if you’re not already bawling as you mash the SAVE button over and over again during the final part of this fight, well... you will".

In Deltarune, Asriel is Kris' brother, but has left for university and is not seen in person.

Papyrus and Sans

Main articles: Papyrus (Undertale) and Sans (Undertale)

A pair of skeleton brothers known for their outlandish human-capturing schemes, Papyrus and Sans function as comic relief within Undertale. They are named after two widely maligned typefaces, Papyrus and Comic Sans, which they use in their dialogue. Papyrus is egotistical yet incompetent, loves puzzles and pasta, and desperately wishes to join the Royal Guard; despite this, he is shown to be a kindhearted and genial character who believes that anyone can be good if they try. Sans is a clever, laid-back slacker and trickster. He often pulls practical jokes and makes puns—he bonds with Toriel over their shared love of the latter. Sans also sometimes breaks the fourth wall.

In Undertale's Genocide route, Sans functions as its final boss, revealing he is secretly an incredibly skilled fighter with control over the game's combat system. Though statistically weak, he uses a unique "Karma" mechanism to deal more damage per frame, and pure speed to dodge the player's attacks. The fight's theme music, "Megalovania", became a widely known Internet meme. In the Papyrus Ending, Papyrus becomes leader of the Underground, with Sans working extensively behind the scenes to keep the Underground stable; Papyrus reveals he is nervous about the job, as he is unaware or in denial that the player killed the other main characters.

In Deltarune, Sans runs a grocery store known as 'Sans, which outwardly resembles "Grillby's" from Undertale with the "Grillby" crossed out. When talking to Kris and Susie in Chapter 2, he refers to himself as its "janitor", despite ostensibly being its owner and cashier. Papyrus is not seen, but most likely still exists, as Sans mentions having a brother, and a flavor text outside of Sans' house references Papyrus's main battle theme "Bonetrousle".

Undyne

Main article: Undyne

In Undertale, Undyne is the powerful leader of Asgore's Royal Guard, as well as leader of the Underground in the Undyne Ending or alternate Toriel Ending. She is a humanoid with fish-like features. While initially presented as intimidating, her clumsy behavior in combat is heavily inspired by anime, which she believes to be an accurate representation of the human world. She possesses a small amount of Determination: a substance that makes humans far stronger than monsters and enables her to persist upon death. It has been theorized this is due to the intervention of her love interest, Alphys, who was conducting experiments on injecting Determination into vessels, such as monsters and flowers, which led to Flowey's creation. Compared to Asgore, who harbors remorse for killing others, Undyne holds a deep hatred for humans and will not hesitate to kill them, although this lessens if the protagonist befriends her.

In Deltarune, she became the town's police chief after Asgore was fired.

Alphys

Main article: Alphys

In Undertale, Alphys is Asgore's Royal Scientist and Undyne's love interest. She is a shy, nerdy, lizard-like monster with low self-esteem, and is a heavy otaku. She created Mettaton's robot body in order to make Asgore think she was capable of creating artificial souls to gain the position of Royal Scientist. She tries to earn the protagonist's trust by helping them "fight" off a malfunctioning Mettaton throughout Hotland, but he later reveals he was acting to make Alphys look better. She is the successor to W. D. Gaster, who served as Royal Scientist until he mysteriously disappeared.

The True Pacifist route reveals that she experimented with Determination on comatose monsters, but this caused them to fuse into creatures known as "Amalgamates". She keeps them locked away in the "True Lab", which is only accessed in the True Pacifist route; it is where she reveals her secrets and resolves to improve her self-esteem. She becomes the leader of the Underground in the Alphys Ending, and is implied to have committed suicide in endings where Undyne and/or Mettaton die.

In Deltarune, she is a teacher at Kris' school and is nervous around Susie.

Mettaton

In Undertale, Mettaton is a robotic entertainer who is the Underground's sole celebrity, hosting various television shows and having products, brands, and a hotel in Hotland themed after him. He is an egotistical glory-seeker and wishes to take a human soul to travel to the surface and become a celebrity among the humans, and tricks Alphys into helping the protagonist reach the CORE so he can kill them under the pretenses of making her look like a hero. It is revealed through diaries in an abandoned house that Mettaton was originally a ghost who dreamed of creating a perfect body for themselves. They achieved this when they befriended Alphys and she created his body (in order to make Asgore think he was an artificial soul), but at the cost of abandoning their cousin Napstablook. In the Genocide Route, Mettaton transforms into a seemingly powerful form called Mettaton NEO, but the player kills him in one hit. In the True Pacifist Route, he reunites with Napstablook, who becomes his sound mixer. In the Mettaton Ending, Mettaton becomes the Underground's dictator, building a cult of personality around himself and making those who do not worship him "disappear", with Sans and optionally Papyrus serving as his bouncers.

In Deltarune, while Mettaton is not seen, he is heavily implied to be the ghost behind the door of Napstablook's house.

Napstablook

In Undertale, Napstablook is Mettaton's cousin, an introverted ghost and DJ. The protagonist battles them in the first area of the game, and can later befriend them at their house in the third area.

In Deltarune, they work as a police officer with Undyne, but do not notice that all of the town's criminals have escaped until the protagonist talks to them.

Mad Dummy/Mad Mew Mew

Mad Dummy is a ghost living in Waterfall, who is presumed to Napstablook and Mettaton's cousin. They seek to become corporeal with their dummy body, which they succeed at in the Genocide Route, becoming "Glad Dummy". They are battled before reaching the more populated area of Waterfall.

In the Nintendo Switch and Xbox ports, they steal a doll of the titular character of the anime "Mew Mew Kissy Cutie" from Alphys's lab en lieu of the dummy and take on the name Mad Mew Mew, believing that it best represents their true form. In the Nintendo Switch port, Mad Mew Mew fights the player character to try and merge with the doll in the Pacifist run if they investigate under Papyrus's sink, engaging in a unique soul mode utilizing the Nintendo Switch's Joy-Con controllers. She appears outside Undyne's house in the Pacifist ending regardless of if she is battled or not. In later ports, she has already merged with the doll without the player's interference.

In Deltarune, they are not seen, but are implied to be a ghost in the same house as Mettaton in Chapter 2.

Exclusive to Undertale

Frisk

Frisk is a child from the Surface and the main playable character of Undertale, who searches for a means to escape the Underground after falling into it. They are not nameable by the player - in an act of misdirection, the player is asked to name the "fallen human" without specifying whether it is the protagonist. In the True Pacifist Route, it is revealed that the "fallen human" superficially resembled Frisk, but had arrived years earlier. Frisk has an androgynous appearance and is a silent protagonist, keeping their true origin and nature ambiguous.

Chara

Chara is a child from the human world, who Toriel and Asgore took in prior to the game's events. Although the player can name them, Chara is referred to as their "true name" on the naming screen. It is stated that they climbed Mount Ebott for an "unhappy" reason and that they hated humanity. Chara enacted a plan to collect six human souls by committing suicide, letting their foster brother Asriel absorb their soul and leave the Underground as one being. The humans fatally wounded them, leading to their deaths and Chara's burial in the Ruins. In the game's Genocide route, Chara is resurrected as a soulless and demonic being who seeks to erase the world, referring to themselves as "the demon that comes when people call its name".

Flowey

Main article: Flowey

Flowey is a flower who initially pretends to be kind-hearted, but is truthfully a sadistic sociopath who adheres to a "kill or be killed" philosophy. He once had the ability to operate outside the laws of the universe via saving and loading save files, like the player character. A powerful, eldritch version of him known as "Photoshop Flowey" or "Omega Flowey" serves as the final boss of the game's Neutral route. If he is spared after his fight as Photoshop Flowey in the Neutral route, he says he cannot understand the player character's kindness towards him despite his threat to murder their loved ones, and gives tips to the player on how to get a better outcome. He is later revealed to be the reincarnation of Asriel Dreemurr, the deceased prince of the Underground. Flowey, like Undyne, possesses Determination, as Alphys injected it into one of Asgore's first golden flowers during her experiments.

W. D. Gaster

Main article: W. D. Gaster

W. D. Gaster, often referred to as "Doctor Gaster" or simply "Gaster", was the former Royal Scientist and created the CORE, the Underground's power system. Following his abrupt and mysterious disappearance, Alphys took up his position. Gaster's presence in the game is hidden, only being directly mentioned in rare Easter eggs and internal game data discoverable through data mining. Despite his near-complete absence from the game, the mystery surrounding the nature of his presence has caused him to gain a sizable fan following.

Events and encounters relating to Gaster are accessible based on an internal code value, labelled "fun", which randomly adds one of several small events to the game at the start of every new playthrough. A few of these events add exclusive characters, called "Gaster followers", who vaguely describe Gaster's history, experiments, and mysterious disappearance, while suggesting he was "shattered across time and space". Though Gaster has no clear canonical appearance, he is generally associated with a warped sprite known as "Mystery Man", which has a chance of appearing when the "fun" value is set to 66.

Through manually editing save data, players can access a hidden room called "room_gaster". This room displays text written in capital letters in the Wingdings font, titled "ENTRY NUMBER SEVENTEEN" (commonly shortened to "Entry 17"), in which an unknown character, presumably Gaster, monologues about an experiment involving darkness. Other elements of the game also hint at Gaster's existence: the weapons Sans wields at the end of the Genocide route are internally labelled "Gaster Blasters", and if the player attempts to name the fallen child "Gaster", the game will forcibly restart, preventing the name from being used. Unused data related to Gaster in the game's files frequently includes the number 6, usually "66" or "666".

It is implied, but not confirmed, that Gaster is involved in the events of Deltarune. The original website for Deltarune, manually archived on the Wayback Machine on two occasions before the game's announcement, featured a portion of Entry 17, and the version number for the "Survey Program" file used to originally distribute Deltarune was "6.6.6". It is also speculated that Gaster is the voice that appears during the game's introductory sequence: the voice speaks using all capital letters and uses similar language to Entry 17; its typer values, which are the game variables that select what font and speaking sound to use, are 666 and 667; and attempting to name the avatar or the player "Gaster" will immediately delete the player's progress. Additionally, a location at the south end of the game's main town emits a distinct sound that plays in "room_gaster" in Undertale, except reversed and slowed down by 666%.

A Deltarune development newsletter emailed to fans on Valentine's Day, 2024, included several randomized valentines purportedly from the game's characters, one of which contained cryptic language and was unsigned. It is occasionally theorized that this valentine is intended to be from W.D Gaster^ , as the valentine mentions "DELTA RUNE" and immediately becomes blank after the newsletter is closed. The valentine might also contain a reference to the poem "The Old Year" by John Clare, which describes a man who disappeared without leaving any "footstep, mark, or place."

Exclusive to Deltarune

Kris

Kris is an androgynous, introverted teenage human who the Dreemurr family adopted and the main character of the game. They are stated to have a trickster personality, and others generally perceive them as a somewhat troubled youth.

While Kris is the player character, there is a separation between Kris as a character and the player as a separate entity. Kris is normally controlled through a red soul that uses the player's inputs, though the player's control can jump to other characters if necessary. Other characters often note the absence of Kris's usual personality during the player's influence, and it is implied throughout the two chapters that Kris harbors their own thoughts and feelings outside of the player, and can outright contradict some of their choices.

Kris is able to remove their soul from their body and exercise free will outside of the player's control, implying it is not their own soul. During the ending sequence of Chapter 1, Kris throws the soul into a birdcage, at which point the player's movement inputs control the trapped soul, not Kris. At the end of Chapter 2, Kris is shown to create a Dark Fountain when not controlled by the player.

In the secret "Snowgrave" route, the player forces Kris into manipulating Noelle to fatally freeze Berdly and many Darkners. In the secret Spamton NEO fight, which is the chapter's final boss when the player is on the "Snowgrave" route, and a hidden boss in the “Normal” Route, the soul can turn yellow and fire shots like the yellow soul in Mettaton EX's boss fight in Undertale.

Lancer

Lancer is the miniboss of Chapter 1, a personified Jack of Spades card who befriends the protagonists and becomes a recurring character in Chapter 2. He is the son of King, the final boss of Chapter 1. He is energetic yet incompetent in his attempts to stop the heroes to earn his father's respect. His gradual developing friendship with Susie is what causes him to rebel against his father.

King

King is the final boss of Chapter 1, a personified King of Spades card and Lancer's father. Originally one of four kings who ruled over the Card Kingdom, he was put in power when the Knight came to their Dark World and overthrew them. He is shown to be a tyrannical figure with little care for his subjects or family, zealously dedicated to the Knight, and plans to take over the Light World as retribution for the Lightners abandoning him. He is also known as ''Chaos King'' or "King of Spades".

Queen

Queen is the main antagonist and final boss of Chapter 2. She is a robot who attempts to capture the party multiple times, although she has no ill will towards them and is mostly friendly, but eccentric. Her full name is "Serial Number Q5U4EX7YY2E9N" and she possesses a gigantic robot called GIGA Queen. She is Lancer's adoptive mother, although whether she is his biological mother is unclear.

Ralsei

Ralsei is the prince of the Dark World, who wears a green robe and wizard-like hat that conceals him in shadow in Chapter 1. He tells Kris of the threat the Dark Fountains pose, and appears to be meek and kind-hearted, encouraging the player to deal with enemies peacefully. When his hat is removed, he is revealed to resemble Asriel, in addition to their names being anagrams.

Susie

Susie is a purple, dragon-like student who is strong and has a gruff, tomboyish appearance and demeanor. She is one of the player's main party members and wields an axe. She starts out aggressive and unwilling to use mercy or befriend people, but mellows out over the course of Chapter 1 and becomes more friendly and boisterous in Chapter 2. She befriends Lancer and Kris, becoming particularly close with the latter, over the course of Chapter 1, while she tends to be playfully snarky towards Ralsei.

Noelle Holiday

Noelle Holiday is a timid fellow student resembling an anthropomorphic reindeer, who is a childhood friend and classmate of Kris and has a crush on Susie. She joins the player's party in Chapter 2. In the Dark World, she wears a white robe and is proficient in magic. The "IceShock" spell can be used to freeze enemies solid, and, if a certain sequence of events is followed, starts the Snowgrave route, in which Berdly is trapped in ice with the eponymous "SnowGrave" spell and she becomes a subservient follower to the player. She has an older sister nicknamed "Dess", implied to be short for December, who is mentioned but never seen physically.

Berdly

Berdly is a know-it-all student resembling an anthropomorphic bluebird who becomes Kris' rival in Chapter 2, and later their ally. It is later revealed that Noelle is smarter than him, but he has continued his snobbish persona to gain attention and praise. If frozen solid in the Snowgrave route, he does not reawaken in the Light World.

Seam

Seam is the first shopkeeper encountered in the game; a nihilistic androgynous Darkner who is a personified cat plushie with a missing eye. Jevil's sidequest reveals they are the former Court Magician, who quit after having to lock up their friend. In Chapter 2, Seam continues to be a shopkeeper in Castle Town and reveals that the superbosses possess powerful artifacts known as "Shadow Crystals", claiming they could make "something incredible" if the player collects them all.

Jevil

Jevil is a Darkner who is a personified Joker card and appears in Chapter 1. He was the former Court Jester and partner of Seam, but was locked away after an interaction with an unknown figure drove him to madness. He began to see his whole world as merely a game and all its inhabitants merely parts of it, influencing Seam to adopt a similarly nihilistic outlook on life. Despite being locked in a cell, he now believes all the other inhabitants of the Dark World have imprisoned themselves and he is the only free Darkner remaining. Upon being set free, he challenges the party to a battle as a "game" and serves as the superboss of Chapter 1.

Spamton G. Spamton

Spamton G. Spamton is a personified spambot Darkner who resembles a marionette and appears in Chapter 2. He speaks in mangled, cryptic English peppered with bracketed marketing keywords like that of a spam email. Spamton has the personality of a used car salesman, and is obsessed with becoming a "BIG SHOT". He often states that he and Kris are alike in some way and that he is trapped as well. He plays a role in unlocking the chapter's hidden route by selling the player the Thorn Ring, and also functions as the chapter's superboss, Spamton NEO, after merging with a defunct robotic body resembling Mettaton NEO. He can also access this form in the normal route by performing certain actions in his shop and in Queen's Mansion. Upon defeating Spamton NEO in the normal route, the player can revisit his shop and speak with his former coworkers, who explain how he rose to success after communicating with an anonymous voice on the phone, who is implied to be the same figure who drove Jevil mad, only to lose his job, home, and sanity when they abandoned him.

Spamton's abilities include shooting money, summoning tiny versions of himself, increasing himself in size, firing lasers and "Pipis", as well as transforming different parts of himself.

On the Snowgrave route of Deltarune, Spamton serves as the final boss of Chapter 2 rather than an optional superboss. This version of the NEO battle is far more difficult, due to a lack of party members.

Spamton also appears as a mentioned-only character in the Spamton Super Sweepstakes, a charity event held by Fangamer. In this, three other versions of Spamton appear (distinguished by middle initials A., B., and Z.), all seeming to be worshippers or relatives of Spamton G. Spamton.

The Roaring Knight

The Roaring Knight is the overarching antagonist of Deltarune. They are a mysterious figure who creates the Dark Fountains and the Dark Worlds they encompass, seemingly to bring about the "Roaring", a prophesized calamity caused by an excess of Dark Fountains creating an imbalance and drowning the world in darkness. King and Queen show great deference to the Knight, regarding them as a figure to worship and emulate. It is implied the Knight possesses enough Determination to create Fountains.

Reception

Griffin McElroy of Polygon described Undertale's characters in general as not just funny, but "incredibly vulnerable", stating that he felt "real affection" for all of them after getting to know them. He called the game his most memorable gaming experience of the year due to his moral compass being guided by this connection. Noting that the characters were "well-written and relatable", he remarked that, when doing the Genocide run out of a desire to see all the game's content, he felt "genuinely terrible".

Richard Cobbett of Eurogamer stated that Undertale's characters were "layered" by RPG standards, calling them "not exactly Walter White in terms of complexity", but more deep than they initially seemed. Using the example of Sans, a "surprisingly complex figure", he noted that "most of the main characters are living with at least one unfortunate past decision or regret". He called the responsiveness of the world and characters an important part of Undertale's success, stating that "spending more time with familiar faces makes them feel real". In a separate review in PC Gamer, he called the game's characters "adorable", saying he had not laughed so hard in years.

Axel Bosso of Bloody Disgusting stated that the game's characters were difficult to trust, causing an anxious feeling with every encounter, starting with Flowey's switch from seemingly harmless to evil. Noting that "even the most inconsequential NPCs have an existential crisis and/or nihilism vibes around them", he said that it was "hard [...] to feel safe in this treacherous environment", though nevertheless remarking that "they became some of my most loved cast in quite some time".