List of Undertale and Deltarune characters
Undertale and Deltarune are fantasy role-playing video games developed by Toby Fox. They take place in different fictional universes, but feature many of the same characters. Undertale is set in a universe where monsters once coexisted with humans, but, after an ancient war, were trapped beneath Mount Ebott and forgotten. The game follows [|Frisk], a human child who falls into the Underground, a large cave within the mountain, and seeks to escape. In Deltarune, considered a spiritual successor to Undertale, humans and monsters still coexist. The main character, [|Kris], discovers the Dark World, an alternate realm inhabited by Darkners, the living representations of real-world objects. 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 have been praised 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
Toriel is among the first characters met by the human, a powerful goat-like woman living in the Ruins. She is the former queen of the Underground, where monsters live, having been married to its king, Asgore. She had a child with him named [|Asriel]. He was killed by humans when he attempted to retrieve human souls to break the barrier, as part of Chara's plan. This led Asgore to slowly collect human souls himself to free the monsters from the Underground and gain revenge on humanity, causing Toriel to leave. She takes the protagonist in after they fall into the Underground and attempts to keep them from leaving due to the worry that her ex-husband would hurt them, but will be either killed or convinced to let the protagonist leave. The protagonist progressively goes through the Underground to confront Asgore, where they're forced to battle. Asgore will only survive in the game's "True Pacifist" route, and will otherwise be killed by either the protagonist or Flowey.As Boss Monsters, once Toriel and Asgore have children, they only grow when their child reaches their age, and cease to grow if the child disappears or dies.
In Deltarune, its main protagonist, Kris, lives with their adoptive mother Toriel, a teacher, while Asgore lives apart from them and lives at his flower shop. In Chapter 3, Toriel ends up in a Dark World but sleeps through the entire adventure. In Chapter 4, an optional cutscene will show Asgore is working on an unspecified plan to clean his name and have Toriel take him back, with several hints implying he'll play a bigger role in future chapters.
Asriel Dreemurr
In Undertale, Asriel is the now-deceased son of Toriel and Asgore, and the prince of the Underground. [|Chara], his adoptive human sibling, convinced him to participate in a plot to collect six human souls from the surface, starting by them killing themself. After absorbing Chara's soul and leaving the Underground, Asriel refused to fight back against the humans who mistook him for Chara's murderer and was killed by them. Asriel was then reincarnated as Flowey by Alphys, 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", serving as the final boss of the route. After being defeated, Flowey returns to the child-form of 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's older brother who has left for college. He has not yet made an appearance in the game, but has been referenced numerous times with characters anticipating his return.
Sans and Papyrus
A pair of skeleton brothers known for their outlandish human-capturing schemes, Sans and Papyrus function as comic relief within Undertale. They are respectively named after the typefaces Comic Sans and Papyrus, which they use in their dialogue, with Papyrus speaking in all-uppercase, and Sans mostly speaking in all-lowercase.Papyrus is egotistical yet incompetent, but is "pretty freaking tough", according to Undyne. Papyrus loves puzzles, and wishes to join the Royal Guard so people would be friends with him. 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, and bonds with Toriel over their shared love of the latter. Sans also frequently breaks the fourth wall. In Undertale "Genocide" route, Sans acts as the final boss, where he reveals some control over the game's mechanics, and uses them against the player.
In Deltarune, Sans runs a grocery store known as 'Sans, additionally working as its cashier, and is shown developing a close friendship with Toriel. Papyrus is referenced, but not yet seen.
Undyne
In Undertale, Undyne is the powerful leader of Asgore's Royal Guard. 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. 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. She notably lacks an eyepatch over her right eye and only knows Alphys in passing. In Chapter 3, Undyne enters the Dark World of the Dreemurr household just in time to rescue the party from the Roaring Knight. However, she is quickly snatched away by the Knight and brought to the shelter south of Hometown, with [|Susie] planning to break into the shelter and rescue her.
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, a location in Undertale, but Mettaton 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". She also created Flowey by injecting Determination onto a flower that had Asriel's dust on it.
In Deltarune, she is a teacher at Kris's school.
Gerson Boom
In Undertale, Gerson is a shopkeeper in Waterfall. He explains that he was once a war hero known as the "Hammer of Justice" in the war against humans, but has since retired. He also mentored Undyne to an extent.In Deltarune, Gerson is an author and historian who had died before the start of the game. However, he appears in the Dark World as the personification of a memento dedicated to him. Throughout Chapter 4, Gerson — known simply as "Old Man" — teaches Susie how to improve her healing abilities and serves as the chapter's secret boss, adopting his "Hammer of Justice" persona to train Susie. He also helps the party defeat a Titan at the end of the chapter.
W. D. Gaster
W. D. Gaster, often referred to as "Doctor Gaster" or simply "Gaster" was the former Royal Scientist before Alphys. He created the CORE, the Underground's power system, which uses geothermal energy to create power. 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.In Deltarune, while he has not yet been seen, various hints imply he is tied to the game's overarching story.