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Characters / Undertale - Spoiler Characters

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Top Index | Major (The Human Child, Flowey, Sans, Papyrus, Undyne, Mettaton, Asgore Dreemurr) | Minor | Monsters | Spoilers (The Fallen Human)

As the name indicates, everyone on this page is a Walking Spoiler, even more than the already spoilery main characters. Even their very existence is a major plot twist. Thus this page contains no spoiler-marking at all. You've been warned. You wouldn't want a bad time, would you?


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  • Walking Spoiler: All of them. All of them are this.
    • The six human souls play a crucial role in beating a major boss. Problem is, that boss is built around trying to make you feel hopeless, so if you know how to beat him going in, the effect is ruined.
    • Asriel, and in particular his existence as Flowey, spoils the pacifist and genocide endings.
    • The Amalgamates spoil much of the pacifist ending since they are only found in the secret area known as the True Lab, where Flowey was created.
    • Chara/The Fallen Child spoils the Genocide ending, and to a lesser extent the Pacifist and Neutral endings as well. Turns out the child from the opening movie isn't the character you're playing as, and in a Genocide run, that first Fallen Child destroys the world.
    • You, as in, being a separate entity from the actual player character, spoils the fourth wall breaking aspects of the Pacifist and genocide endings
    • W.D. Gaster and his followers are characters hidden in the game's code with an unclear identity.

    Human SOULs
You're filled with DETERMINATION.

The six humans who fell down into the underground before the Player Character did. Their SOULs were harvested for the sake of breaking the barrier imprisoning the monsters and exterminating the human race. You can find their old weapons and armour scattered throughout the world.

  • And I Must Scream: They're seemingly unable to do anything while they're trapped in the SOUL jars.
  • Ambiguous Gender: Like Frisk and Chara, their genders are never revealed.
  • Ambiguously Evil: One of them (the blue SOUL) likely killed at least one monster, possibly more, but we have no idea why or how.
  • Asshole Victim: Maybe some of them. It's implied that at least a couple of them managed to rack up a lot of EXP before they were killed, most prominently the blue soul (whose items are described as "dangerous" and covered in dustnote ) and the yellow soul (who had a real gun). It's left ambiguous, however, if they did this for actually malicious reasons, or if they did it out of (legitimate, since unlike the player character they only have one life) self-defense, or a desperation to avoid being killed and forcibly used as a weapon to destroy everyone they love.
  • Barred from the Afterlife: Forced to stay rooted in the mortal world after death through unexplained technology. In the Neutral and Pacifist endings, they're all finally set free.
  • Big Damn Heroes: After calling out to them enough, they resonate with Frisk and begin turning the fight against Flowey. And when he uses his save state powers to undo his defeat, they unite to utterly destroy him in one shot, saving Frisk from a truly unwinnable situation.
  • Chef of Iron: Implied of the green SOUL, who used a frying pan as a weapon and wore an apron.
  • Colour-Coded for Your Convenience: Separately from your red SOUL and grey monster SOULs; they come in orange, yellow, green, cyan, purple, and blue. Notably, the colors correspond to the various colors that bosses can turn your SOUL, as well as the three different attack colors.
    • The colors are indicative of the humans' greatest virtue before they died:
      • Cyan - Patience
      • Orange - Bravery
      • Blue - Integrity
      • Purple - Perseverance
      • Green - Kindness
      • Yellow - Justice
  • Dance Battler: The blue SOUL was, which explains why ballet shoes are a weapon you can acquire.
  • Determinator: The purple SOUL's special trait was perseverance. Though obviously they weren't as determined as Flowey or Frisk.
  • Empathic Weapon: Even after death, they can still feel emotion and respond to your fight against Flowey.
  • Everyone Has Standards:
    • Despite their rather unclear morality, all of them aid you during the battle against Flowey and eventually rebel against his control to save you.
    • Also, one of the rare things that's sure about them is that they all met Toriel in the Ruins. Since she's still there at the beginning of the game, none of them harmed her. Therefore, even the more morally ambiguous of them never thought of harming her, let alone doing a Genocide Run.
  • Fatal Flaw: Can be inferred, judging by the location and effects of their equipment and/or their SOUL modes.
    • None of them had enough Determination to LOAD or SAVE (at least, not enough to surpass Flowey's), meaning they only had one life to live. Once they died, that was it.
    • Cyan: Cyan attacks in the game are dodged by standing still, implying that a cyan-colored SOUL won't move or dodge attacks. Cyan's journey was the shortest, and their equipment is found in the Ruins, the earliest part of the game. That, or they were too patient. They waited in place absolutely sure that they'll be saved and starved to death.
    • Orange: Orange attacks are dodged by moving through them. An orange SOUL would be constantly moving around and unable to dodge cyan attacks, which are used by the guard dogs in Snowdin. Additionally, the Ball Game mentions them "rush[ing] fists-first through all obstacles", implying that they were reckless and got in over their head, leading to their death.
    • Blue: A blue SOUL is affected by gravity and can only make short jumps before falling to the bottom of the bullet box. Many enemies in Waterfall, where Blue's equipment is found, have attacks that are difficult to dodge at the bottom of the box (Aaron's CHECK text even says as much).
    • Purple: Their equipment increases invincibility after taking damage, requiring them to get hit in order to make the best use of their weapons. They likely allowed themself to get hit too many times and died.
    • Green: The green SOUL mode makes the player's soul immobile and allows them to block attacks from a single direction. Their equipment is found in Hotland, where there are multiple enemies (Pyrope, the Royal Guards) whose bullets come from all directions. Even then, their equipment's perks also suggest that they were over-reliant on healing items mid-battle and likely ran out of supplies at the worst possible time.
    • Yellow: They had a gun for a weapon and possibly made it the farthest (along with Green), but it's empty when the player gets it, implying that they lost their last line of defense when they ran out of bullets. Whoops.
  • Frying Pan of Doom: The green SOUL's weapon.
  • Hero of Another Story: Or Villain of Another Story, depending on whether or not they (or some of them) actually were evil. They fell into a predicament similar to Frisk's and, just like them, they went on a quest to try to go back in their world. However, they are already dead when the game begins, leaving behind them a few items and very few clues on what their stories were.
  • Hot-Blooded: The orange SOUL, judging by their associated trait, Bravery, and the flavor text in the Ball Game.
    Ball Game, orange flag: You are the kind of person who rushes fists-first through all obstacles.
  • Human Sacrifice: They were killed to make someone powerful enough to break the barrier.
  • Improbable Weapon User: Including ballerina shoes, a notebook, and a frying pan.
  • Killed Off for Real: They fell in various points during the Underground, it's implied the farthest any of the other souls made it was Hotland (the green and possibly the yellow one, depending on where Catty and Bratty got the yellow SOUL's equipment from).
  • Knife Nut: The cyan SOUL used a toy knife, which can be found in the Ruins.
  • Leitmotif: A different remix of "Your Best Friend" for each of them plays when they are fought during the confrontation with Photoshop Flowey. Cyan's and Orange's versions are higher-pitched than the original, Purple's and Yellow's versions are lower-pitched, Blue's uses a whistle instead of chiptune, and Green's uses a piano.
  • Living MacGuffin: Not so much living anymore. Still semiconscious, though.
  • Mysterious Past: All that is known of them are the weapons and armor they left behind and what can be inferred from the color of their SOULS. How and why they ended up in the Underground, how they died, and even if they were children like Frisk and Chara are completely unknown.
  • Nice Hat: The Cowboy Hat belonged to the yellow SOUL.
  • Playing with Fire: Getting past the green SOUL during Photoshop Flowey's fight requires dodging waves of flames tossed from three frying pans.
  • Plot Coupon: They're six differently colored (but otherwise identical) objects that are being collected in order to accomplish a goal, which clearly resembles a common type of plot coupon in RPGs. The difference with these? You're not collecting them; the monsters are, and the player character happens to be the last one they need.
  • Posthumous Character: All of them died and their souls were taken by Asgore before the game began; the exact circumstances of their deaths, either at the hands of Asgore himself or someone else, isn't stated.
  • Power-Up Food: When turned to Frisk's side, the green SOUL tosses healing bullets shaped like fried eggs.
  • Rainbow Motif: Together with Frisk's red heart. This also pops up in with 7 coffins with the same color hearts (with the red one being closed), and with Photoshop Flowey cycling through the entire spectrum in his demise.
  • Riddle for the Ages: Why did they climb the mountain and fall into the Underground, what were their personalities like, and how did they die?
  • Ripple Effect-Proof Memory: Them having this is the only saving grace in the Photoshop Flowey fight. Even if you die and Flowey reloads, they remember that you've called to them, and they still want to help you. This contributes to them rebelling after you "defeat" Flowey and he reminds you that he can just reload back to full health.
  • Shout-Out: Much like Frisk's Stick, their weapons, with the exception of the Torn Notebook, belong to classes of Mother weapons:
    • Toy Knife: Teddy from the first game had knives as his first two weapons, though these would be outshone by a Sword and Katana.
    • Tough Glove: Kumatora from the third game used gloves.
    • Ballet Shoes: Duster from the third game would kick with his shoes, though none of them were ballet shoes.
    • Burnt Pan: Ana and Paula from the first two games fought with frying pans.
    • Empty Gun: Lloyd and Jeff, also from the first two games, wielded guns.
  • Take Up My Sword: All of the Gear in the game, with exception to the Temmie Armor and the items in New Home were gear used by them before they died. In the battle against Flowey, it is even shown in attack phases which colored soul used which weapon:
    • Cyan = Toy Knife and Faded Ribbon
    • Orange = Tough Glove and Manly Bandanna
    • Blue = Ballet Shoes and Old Tutu
    • Purple = Torn Notebook and Cloudy Glasses
    • Green = Burnt Pan and Stained Apron
    • Yellow = Empty Gun and Cowboy Hat
  • Unknown Character: Despite their importance in the story and the Neutral and True Pacifist Endings, almost all information on them is either implied or completely left for interpretation. Even their names are unknown, as in the room with their coffins, only Chara's can be readnote .
  • What Happened to the Mouse?: They're mentioned as missing in the Neutral and True endings, but what happened otherwise is unexplained. Simple Logic would state that in a Neutral ending, the only person there is Frisk, and Humans cannot absorb Human souls, nor can Monsters absorb Monster souls. This means that they just fade away after being released from their Soul Jar. In the True Pacifist ending, Asriel says that he can't bear to keep the souls imprisoned within him, and lets them all go, the six human souls included.
    • If you return to the room with the coffins at the end of the True Pacifist route, you find that they're all now open. Make of this what you will.

    The Amalgamates
no No NO NO NO NO NOnote 

A group of abominations created by accident from a terrible experiment involving Determination.

  • Alien Geometries: Assuming its sprite is meant to be taken literally, Endogeny appears to somehow have a series of dog faces and bodies in the negative space between its legs.
  • And I Must Scream: All of them (especially Lemon Bread) are at least slightly aware of their plight, but they can't do anything about it due to Alphys keeping them a secret, and they can't die by normal means.
    Lemon Bread: Welcome to my special hell.
  • Assist Character: The Reaper Bird doesn't attack directly; it instead has the help of "Everyman", a bird-like humanoid that attacks in bizarre ways.
  • Big Friendly Dog: If you coax Endogeny over, you can pet it like the other dogs. It's described as being very affectionate in some of the quotes.
  • Blob Monster: Endogeny is described as being amorphous, and is a vaguely dog-shaped blob that can disperse itself into floating particles.
  • Body Horror: Several "normal" monsters combined into one.
  • Call-Back: By the time you face them, you'll likely have faced all of their "components" earlier in the game. The method of Sparing them tends to be similar. Special mention goes to Endogeny, whose Spare method is exactly the same as that of Greater Dog. Once it's pacified, the background music changes to "Dogsong", which played in the fight against Greater Dog.
  • Came Back Wrong: The result of Alphys' experiments with injecting monster souls with Determination.
  • Dark Is Not Evil: They're terrifying to look at, the reason behind their existence is horrifying, and the sequence in which you meet them is probably the closest the game ever comes to being a straight-up horror game... but none of them seem to sincerely want to hurt you (outside of maybe Lemon Bread, and even then that's more you being the first target for... their... frustrations in years), they all back off once Alphys tells them to, and at the end of the pacifist route, their happy ending is simply being with their families again. They're creepy, sure, but not truly malevolent, or are only truly dangerous should you panic and not attempt to understand them.
  • Detachment Combat: The Reaper Bird's Everyman can send its head flying at your SOUL. Actually, make that about a dozen heads at once.
  • Dual Boss: The Memoryheads are a triple boss, but in practice it's just one enemy, as you can't kill them and they're all Spared at the same time.
  • Expy:
    • Lemon Bread has a similar name and design to Melon Bread, a boss from the Genesis game Gunstar Heroes.
    • The Memoryheads resemble Giygas.
    • As a whole, they are amalgamates of the chimeras from Mother 3.
  • Eye Scream: Snowdrake's Mother has Vegetoid faces in the place where a Snowdrake's eyes would be.
  • Final-Exam Boss: Hopefully you remember how to spare the monsters in the previous areas; you'll need to if you want to get past these guys.
  • Frankenstein's Monster: Are quite similar, such as being the result of an experiment to cheat death, being composed of multiple corpses, and their creator being horrified of what she created. Unlike the original one, however, they ultimately get a happy ending.
  • Genetic Abomination: Although ultimately Lovecraft Lite, their powers are definitely more on the Eldritch Abomination end of the fence. Their encounters play out like video game glitches, with bizarre names and strange dialogue. The Memoryheads' ACT options are your menu buttons until you use the "CALL" command. The Reaper Bird's flavor text and dialogue is multiple overlapping lines of text, and is initially only called ",". Lemon Bread's dialogue comes from 12 separate speech bubbles covering the top of the screen. If you try to ignore Endogeny, the flavor text says he appears everywhere you look, and trying to talk to Snowdrake's Mother will often result in the dialog box describing you as doing things much more extreme than the command suggested.
  • Gone Horribly Wrong: They originated as an experiment by Alphys to infuse dead monsters with Determination. To say it didn't go as planned is a gigantic understatement.
  • The Grotesque: Despite their horrific appearances, they turn out to be no more violent or evil than any other enemy you've faced throughout the game. Alphys eventually decides to quit keeping them a secret and lets them join the other monsters in the Underground, where they seem to get along peacefully enough.
  • Knight of Cerebus: Their appearance marks one of the darkest and scariest segments of the game and its backstory.
  • Lovecraft Lite: While they are quite horrific to look at and possess bizarre glitch-like abilities, they won't drive you insane when you look at them and are further disqualified from full Lovecraftian status by, well, being rather nice once you get to know them. The Memoryheads especially tell you "Come join the fun", but when you refuse they just say "Oh well" and "It's a real get together" and leave you in peace. Heck, if you decide to sleep in one of the lab's beds, an amalgamate (not pictured) will tuck you in and pat you on the head.
  • Meaningful Name: Lemon Bread is named after a type of pudding, and one of its constituent parts is Moldbygg, a gelatin monster.
  • More Teeth than the Osmond Family: Lemon Bread, whose teeth are actually made up of pieces of a Moldbygg. Their face consists of two angry eyes (which are Aaron tails) and a huge mass of gelatinous teeth. Their attack also consists of lots of teeth trying to crush your SOUL.
  • Mythology Gag: In The Halloween Hack, another one of Toby Fox's games, a trio of minibosses replacing the Krakens called the "Amalgamates" shows up in the late-game, and has the same base idea as the Amalgamates in this game (several monster parts combined to create one new monster). However, the Amalgamates in Undertale are important to the story, rather than generic baddies, though both are the last set of minibosses before the Final Boss.
  • Named by the Adaptation: Deltarune gives the names of several of the Amalgamates' before they became what they are. Snowdrake's Mother is named Crystal, one of the dogs in Endogeny was named Muttler, and Shyren's sister in Lemon Bread was named Shyra.
  • No Biological Sex: Ambiguously either played straight or Inverted. Many of them are composed of both men and women, such as Lemon Bread, who is both Shyren's sister and Aaron's brother. The game never elaborates on how (or whether) this works out.
  • No-Sell: They're completely unable to dienote : trying to attack any of them just causes random red text to quickly flash by instead of damage numbers, and the HP bar of the one you attacked extends beyond the dialog box afterwards. Fortunately, this means you can't ruin your Pacifist run by accidentally killing one. While Snowdrake's Mother does take damage from attacks normally, she's still unkillable as her health regenerates at the start of each turn.
  • One-Letter Name: In-battle, Reaper Bird's name is rendered as a single comma.
  • Our Ghosts Are Different: They are essentially undead monsters.
  • Poison Mushroom: The Memoryheads can give you a Bad Memory if you perform the Item ACT on them. It damages you for 1 HP if used, but it's a full heal at critical HP.
  • Punny Name: Endogeny. It's comprised of the parents of the Royal Guard dogs.
  • Recurring Extra: Reaper Bird's Everyman, named "strangeman" in the game's files, has two suspicious appearances in Deltarune — as a cameo on the Bonus Boss' attack patterns of all things and as grafitti on the Light World. Toby Fox referred to him both on Twitter and the artbook as "Just a good guy that shows up on occasion", as if suggesting some kind of importance...
  • Treacherous Checkpoint: Lemon Bread, which is disguised as a Save Point until you interact with it, is the page image.
  • The Unintelligible: The Reaper Bird begins speaking with multiple dialogues overlapping over each other. It eventually separates into the individual components if you spare it. The Memoryheads can also speak in a horrible distorted screech that resembles a dial-up modem, but comes in fine through the cell phone.
  • Voice of the Legion: Lemon Bread's dialogue consists of 12 different speech bubbles cover the screen with the same dialogue.
  • Voluntary Shapeshifting: They disguise themselves in a variety of ways, such as being water in a sink (Memoryheads), a refrigerator (Snowdrake's Mother), floating particles (Endogeny), a save point (Lemon Bread), and even your '!' balloon (Reaper Bird). Save for Endogeny, the forms they take in their overworld sprites are also nothing like the ones they use in-battle.
  • Was Once a Man: All of them used to be multiple monsters. Monster bodies don't have the same physicality as human bodies, so their transplanted Determination caused their bodies to melt and fuse together instead of simply allowing their souls to persist after death.
  • Weaksauce Weakness: Endogeny is a dog, so the Stick will instantly pacify it as it does with all other dogs. If you already used your Stick, then the Hush Puppy you can get at the hotel has the same effect.
  • What Happened to the Mouse?: The Memoryheads and Reaper Bird completely disappear from the story after you deal with them in the True Lab. This is because neither of them are shown to have any family in the Underground, unlike the other three Amalgamates.
  • You Cannot Grasp the True Form: Definitely gives off these vibes, especially since their battle music takes a sample from the Trope Namer. For example, before reaching Spare conditions, Reaper Bird's name is given as a single comma, and the Memoryheads are completely incomprehensible unless communicated to through your cell phone.
  • Zero-Effort Boss: Snowdrake's Mother tries to attack, but she's so messed up that she can only fire slow projectiles that deal low damage. Sometimes, they don't even make it to the dodge window. She's also one of the easier Amalgamates to Spare.

    The Anomaly 

Thought you were just the Player Character here? Nope! Frisk and the player are implied to be separate entities in Undertale; the latter simply dictates the actions of the former. But remember that Undertale isn't a typical RPG; all of your choices will affect the game world... for better or for worse.

Depending on the interpretation, you either play as the Fallen Child (see their page) or yourself. Either way, this page describes the role of the Anomaly.

  • Above Good and Evil: Since the world of Undertale is fictional and you're not, you are essentially this. However, the game will attempt to tell you that you aren't, especially in the No Mercy route.
  • Abstract Apotheosis: As noted in Sentient Cosmic Force, you’re a being only visible in consequences that happen in the timelines, you are the driving force in the world, it’s your choices and determination that replaces Frisk's. Thus (if perhaps only in the “purity of action” sense of the trope or perhaps something more literal), you are not just a Determinator, you are DETERMINATION itself.
  • All-Loving Hero: It's very easy for a pacifist player to take this route.
  • Ambiguously Evil: One of the game's primary artistic purposes is opening up questions about human morality regarding how they treat circumstances where actions have supposedly no consequences. Stereotypes aside, odds are you're not actually an evil person; you just wanted to see what would happen if you killed everybody or only killed certain people. The question here is whether or not these actions actually have any true moral significance — not to the point where it's worthy of real-life reprimanding, obviously, but still enough to make the player introspect and question themself and their actions.
  • The Antichrist: In the Genocide run. You fit the archetype regardless if you’re playing as Chara or not. A figure of unending destruction who helps bring about The End of the World as We Know It.
  • At Least I Admit It: Post-genocide, should you try to play the game again, Chara will claim that you actually believe you're above consequences. There's nothing stopping you from outright admitting that's the case, and indeed, the only way to keep playing without permanently tainting the Golden Ending is to modify the save files in order to subvert the very consequences the game had in place for you.
  • As Long as There is Evil: The fact that you exist and can reset the game at any time — erasing all the progress and memories made — theoretically makes you the single most potentially evil — and unstoppable — entity in the story.
  • Ax-Crazy: Hoo boy… In the genocide run and the darker neutral runs, you are one of the biggest examples in videogame history; after all, name one character who tediously hunts down an entire country and kills them one by one, and if you choose to erase, destroys the entire gameworld. Majin Buu and Omega would be proud. Emphasis more on the ax than the crazy, as in real life you’re likely much more sane and kind, hopefully.
  • Big Bad: During a Genocide run. If you are playing as yourself and not the Fallen Child, they will take control by the end of the Genocide route, forming a Big Bad Duumvirate with you, though only for the Fallen to pull an Eviler Than Thou.
  • Big Good: You are this during a Pacifist run.
  • Blood Knight: Many a player has been convinced to do a Genocide run for the sole purpose of doing battle with Undyne the Undying and Sans, seeking a new, harder challenge.
  • Blue-and-Orange Morality: There's a creature in the game's canon that exists outside the universe. This creature can't manifest into the world by itself, but it can take control of a host and puppet them around. Whether it befriends everyone or commits systematic genocide, this creature does it just to see what will happen. It remembers everything that's been done to it, in all timelines, even when their host body has been destroyed numerous times. Only monsters with Medium Awareness like Flowey and Sans even know this creature exists. What is this creature? It's you.
  • Combat Sadomasochist: On Genocide route, Sans will accuse you of being this if you defeat him, reload, fight and defeat him again. Considering you went through hell and did it one more time just to see his reaction...
    "... you're really kind of a freak, huh?"
  • The Corrupter:
  • Cosmic Chess Game: You're a player for once instead of a pawn; your opponent is Flowey, the only other character to use determination and who flat-out calls it a game, and also possibly Chara, though they will normally remain submissive to you.
  • Cosmic Horror Story: You can easily turn the entire game into this if you so choose. There is no character within the game, not even Flowey or the Fallen Child, who can match the sheer cruelty you can inflict upon the world. Arguably, the game is this merely by virtue of the player's relationship to it, regardless of how they actually use their power.
  • Cosmic Plaything: You become this if you sell Frisk's soul to Chara. You're allowed to start over, do pacifist, neutral, or genocide... all under the fallen human's constant supervision. Though you can, of course, completely avert this at your own discretion if you decide to modify the saving files.
  • The Dark Side: You are the Dark Side, feeding Chara power and corrupting them into evil and being the Antichrist to your Satanic Archetype at the same time. (Only in the genocide run or when you kill somebody, really.)
  • Determinator: You have to be to get one of the true endings, or even make it to the end after all the deaths you’ll get; determination and the resolve to achieve what you want is one of the game’s main themes, and it’s heavily encouraged in players to match Frisk and the Fallen Child.
  • Dragon-in-Chief: Depending on how you see Chara and their relationship with you, either you are this to them or they are this to you, or you're on equal terms.
    • It's the Fallen Child's LOVE and stats Frisk (and you) are using.
    • It's you who actually does all the work, dodges the attacks, etc., with Chara simply providing the muscle and information.
  • Dramatically Missing the Point: Plenty of players have gloated about how they've outsmarted Chara by, after completing a Genocide Run, editing the game files in order to give themselves their Golden Ending back, thus proving that they don't "think" they are above consequences, they are above consequences... all while completely overlooking the fact that them doing this proves that they acted in exactly the way Chara has predicted them to: refusing to accept any kind of lasting negative consequences for what their own actions did to the game. In fact, answering Chara's accusation that you believe you're above consequences with a blunt "yes" simply has them agreeing with you.
  • The Dreaded: It's perfectly possible to be this even though everyone will think you’re Frisk, but well, basically the entire underground will fear you.
  • Eldritch Abomination: A being beyond comprehension, the same species as the creator of the world, utterly beyond punishment and capable of altering reality with ease. Powers include possessing Frisk, returning lost beings back into existence, resetting the world and, yes, even undoing what cannot be undone. No one can understand why such a being would do what it does.
  • Empowered Badass Normal: A normal human, armed solely with your determination and your skills as a player and possibly a hacker, given a computer, an Undertale program and Time Master and Demonic Possession powers over Frisk and the game world. That's all you need to fight and defeat/conquer even the greatest opponents and challenges the game has to offer, such as Sans and Undyne the Undying.
  • Eviler Than Thou: When it comes to Flowey and Chara in a Genocide route:
    • By the end of the route, Both you and Chara turn on Flowey and by the end chop him to pieces. A short conversation later, Chara pulls this trope on you.
    • Invoking this is about the only way you can get a semblance of victory over the Fallen Child, baffling them with your sheer depravity.
    • Have you done a Genocide Run but don't want to sell your SOUL? Don't even bother to open the game again after Chara crashes it. Just straight up uninstall it right then and there (And if you ever want to play it again, you may reinstall it). If you do that you can pull this trope on them.
  • Evil Is Not a Toy:
  • Expendable Alternate Universe: Want to keep playing the game, even after getting the Golden Ending, and Flowey asks you nicely not to? Just copy your save files! Everyone gets to keep their happy ending, while you still get to have fun...
  • Face–Heel Turn: Any player who gets the True Pacifist ending, then resets and starts a Genocide run pulls one. For a while, you still have a chance to turn back.note 
  • Fighting a Shadow: The main reason why no one can hurt you, no matter how badly they want to. You’re in Real Life, a literal higher plane of existence, using Frisk as your avatar in the game world; how are they supposed to reach you, much less do you harm?
  • From Nobody to Nightmare: If you choose to take the No Mercy run, you go from attacking common monsters to mutilating bosses in one hit to destroying the world with help from the fallen human.
  • A God Am I: Invoked. Flowey will call you out on your attempts to shape destiny.
  • Greater-Scope Paragon: In a meta sense. Since Frisk is the main character and Sans and Toriel are both technically the Big Good, that technically makes you the greater scope paragon of the entire game, since you're technically responsible for most of what Frisk does in the story... assuming that you aren't going for a genocide run, of course. That being said, on the flipside...
  • Greater-Scope Villain: ...Also in a meta sense. With the Narrator Chara theory gaining more and more supporters, the Undertale fandom in general has come to the consensus that it's not Chara's fault — it's yours for making Frisk do the genocide route and causing the world's destruction. These days, you'll find much more YouTube comments along the lines of "Chara is evil in a Genocide Run, but so are you and/or you made Chara that way!" than the latter. Heck, there's even a YouTube video out there with the song "When You're Evil" regarding the player, not Chara. Given that there's no Word of God on the issue currently though, it's all open to interpretation, much like many other aspects of Undertale. This trope only applies if you're going for a No Mercy/Genocide run.
  • The Hedonist: Sans in a No Mercy run accuses the Anomaly of never being happy, always wanting more.
  • Heel–Face Door-Slam: Interestingly enough, this only ever happens to you, the player, in the aftermath of a genocide playthrough. Once you've done this, and sold your soul to recreate the world, you will never have a true Golden Ending again without cheating. For everyone else, though, this trope is averted and characters who have done terrible things will be forgiven, since, well, that's what the game is about. Alphys, who's responsible for innocent monsters being turned into the molten-together and horribly disfigured Amalgamates, gets fired from her job when she tells the truth, but since monsterkind is about to leave the underground anyway, this won't actually be a bother — and her friends continue to be by her side anyway. Asgore, who has the blood of six human children on his hands, is still a respected leader. And in most cases, you're the one to show mercy, like with Undyne or Flowey.
  • Heel–Face Revolving Door: A player who goes through several runs choosing a different route each time is essentially this.
  • Heel–Face Turn:
    • The game allows a player on the Genocide path to step off it up until the Mettaton NEO fight. When Papyrus, for example, offers to Spare you, it's a genuine offer with no strings attached, and will revert your game to a Neutral one. Sans' offering, on the other hand, is not.
    • It's possible for the trope to still be played straight after the player accepts Sans' false offer of mercy, if the player takes the skeleton's words to heart and RESETS after getting dunked on. Of course, this depends entirely on you.
  • He Who Fights Monsters: Literally on the more malicious runs.
  • Hijacking Cthulhu: From the moment you start Undertale, you've unwittingly seized the power to SAVE and RESET away from Flowey/Asriel, and he really doesn't take kindly to this.
  • Horrifying the Horror: If you finish at least two No Mercy runs, even Chara won't be able to understand your actions.
  • Humans Are Cthulhu: Everything in the game world is up for your own amusement. There's absolutely nothing the entities within can do to harm you. Even when Chara pulls an Eviler Than Thou to screw you over beyond the fourth wall after a No Mercy run, you can screw them over beyond even that by actively editing the game's codes. Sufficiently informed, you can manipulate anything in the game.
  • Humans Are the Real Monsters: Should you decide to go full Genocide or kill almost everyone in a more neutral route.
  • Humanoid Abomination: In Undertale, the line between Chara, Frisk, and the player gets extremely blurry, so their “inhuman” descriptions in the Genocide Route should probably be taken to include you. If that is not eldritch enough, see the Eldritch Abomination entry, so yeah, you fit straight here, especially in No Mercy; has it even occurred to you that maybe, just maybe, Chara is able to take your (or Frisk's) SOUL because you turned demonic and not them.
  • Incorruptible Pure Pureness: The player who chooses to go full pacifist, ensuring the happiest of endings, and never play the game ever again (or watch anyone else play the worst endings), achieves this trope.
  • Invincible Hero: If you're truly Determined to give as many characters as possible their happy ending, or to slaughter the entire Underground, then there's nothing anyone can do to stop you; Flowey will become just a minor irritation, as will all your possible deaths. In a greater sense, you yourself are literally invincible, as you exist in a different dimension than the characters.
  • Invincible Villain: There is also nothing the characters can do to stop you from doing a Genocide run, aside from trying to talk you out of it or hoping you'll get bored and give up. With your Determination, every defeat is just a setback. The only one you can't beat, without manually altering game files, is the Fallen Child after you've sold Frisk's soul to them.
  • It Amused Me: During the final battle of the Genocide route, Sans will start speculating on your motivation for all the evil things you've committed. At first he considers that you might simply enjoy killing things, but then brushes the idea off as ridiculous, saying that "you're the kind of person who won't EVER be happy". He then goes on to accuse of you of this trope, saying that you're not even motivated by good or evil anymore, you're just doing this because you can. And because you have that ability, and are seemingly above consequences because of your ability to SAVE, you just can't help yourself. It's a gamer's natural desire to seek out and accomplish everything in a game, after all.
  • I Want My Beloved to Be Happy: If you listen to Flowey and choose to abstain from a True Reset after getting the Golden Ending, letting the characters you've grown to know and love happily live out the rest of their lives without you. Believe it or not, quite a few fans will admit to having done this.
  • Karma Houdini: No matter what bad thing you will do, the in-game characters will be the one punished. Nothing bad happens to you.
  • Knight of Cerebus: In a Genocide run.
  • Lack of Empathy: To get the Genocide ending, not attaching yourself to the characters in the game is pretty much a given necessity.
  • Lovecraft Lite: Despite all those horrifying things that you can do in the game to this world and its people, nothing can make you do them. It's possible to achieve the Golden Ending without killing anyone... and even if you want to replay the game, you can always abstain from the No Mercy route and achieve the Golden Ending again.
  • Mistaken Identity:
    • If you believe you are playing as yourself and not the Fallen Child , then any time Flowey addresses you as the Fallen will count as this.
    • A subtle example in Sans. He seems to be the only character (aside from possibly the Fallen) who confirmably knows that you even exist — but while he correctly identifies you on a Genocide run as the cause of the latest resets, he doesn't seem to realize that you haven't always been the one resetting the timeline. Flowey's speech a few rooms earlier gives the impression that his reign as resetter was a Time Abyss; most likely, he was responsible for far more loops than the player ever could be. Sans never seems to realize this. However, it's not clear whether the "anomaly" in question is Frisk or the player since it's unclear who's truly in control of all resets.
  • My God, What Have I Done?: The game tries very, very hard to evoke this feeling out of you the entire time you play the Genocide route, and during worse Neutral endings, in the hopes you'll Reset.
  • No Challenge Equals No Satisfaction: It's the aspect about you that Sans fears most. You're neither doing anything good because it's the right thing to do, nor anything evil for sick pleasure — but simply because it's a challenge. And because you can achieve it, you may feel required to.
  • No Kill Like Overkill: Your damage becomes ridiculously excessive in the Genocide route.
  • Nominal Hero: You don't actually have to feel sympathy for the inhabitants of the underground, but can still go through with the Pacifist ending because you find it to be an obligation. (Which it is, if you want the final ending.)
  • Omnicidal Maniac: In a Genocide run, the Anomaly decides to kill every single living creature it can, despite the fact that none of its victims can even begin to hurt the Anomaly.
  • Omniscient Morality License: Since you have the ability to go back and fix things whenever you want, just like any other video game, you essentially have omniscient control over the game's universe and may be tempted to succumb to this. If you do, you'll be faced with quite a bit of harsh deconstruction.
    Sans: sometimes... you act like you know what's gonna happen. like you've already experienced it all before. this is an odd thing to say, but... if you have some sort of special power... isn't it your responsibility to do the right thing?
    Sans: heh. well, that's your viewpoint. i won't judge you for it. ... Y o u d i r t y b r o t h e r k i l l e r.
  • Outside-Context Problem: Your ability to SAVE and RESET are extremely rare abilities in the game's setting, but certain characters can use them. Your ability to alter the game's data, however, is something none of them could ever replicate. On another level, you're a being from outside the universe that none of the characters could have ever predicted would have shown up and whose nature is inherently different from all of them. They can do nothing to stop you no matter what you do, as you operate on completely different rules than they do.
  • Pay Evil unto Evil: You can take the game's story and characters 100% seriously and still choose to kill some of the more aggressive monsters if you think they deserve it.
  • The Perfectionist: If you're trying to do a specific playthrough, yet reset or save scum after every screw-up. Flowey may even call you out on it depending on the circumstances.
  • Person of Mass Destruction: As Sans describes it, a Genocide path will not bring you any kind of satisfaction, you'll just keep consuming timeline after timeline.
  • Player and Protagonist Integration: You start controlling Frisk as a Heroic Mime, and in most playthroughs, that is all that you are. By the end of each route, it's implied you're separate entities: either you are playing as the Fallen controlling Frisk,or as yourself.
  • Pure Is Not Good: Your determination will need the japanese virtue of Makoto if you want to get an specific ending, this includes the Genocide Run. Sans says this evil purity is the most dangerous part of you.
  • Reality Warper: You can delete and edit the game’s files, which clearly makes you this in a meta way, and, as said everywhere else, Undertale is a very meta game on purpose — then there's the ability to reset...
  • Redemption Equals Death: If you take Sans up on his offer of friendship at the end of the No Mercy run, he'll kill you and tell you that if you were sincere about being friends, you'll never come back. Though this is an interesting twist on the trope because Sans is well aware that you're unkillable you can't be Killed Off for Real because you can control time, so his saying that doesn't mean "stay dead", he's telling you "reset and be a better person".
  • Satanic Archetype: Genocide Anomaly is the best example. A pure evil Eldritch Abomination (The same species as The Maker) who rebels against The Creator of the game's desire to free Monsterkind out of Pride and your own selfishness, abandoning all notions of goodness and consigning yourself to the most evil route by becoming The Angel of Death (Which is one of Satan's many monikers) and creating an Antichrist (Who you serve as The Corrupter to) to serve as your Earthly envoy and agent of destruction. Players who did a Pacifist Run first also fit the Fallen Angel and Fallen Hero tropes, and even invoke a bit of Demonic Possession during their control of Frisk. Out of all the characters, the Player (You) are the closest thing to Satan.
  • Screw the Rules, I Have Supernatural Powers!: You have the power to SAVE, and reset, time itself, if you so choose. However you're not the only character who can handle that raw kind of power; Asriel and Chara will try to wrestle it back from you, and with the latter it's for keeps. Though the fact that you can go a step beyond and edit the files of the game means that your powers will (in a meta sense, anyway) always outclass Chara's.
  • Sentient Cosmic Force: An interpretation, as you’re a being only visible in consequences that happen in the timeline; you are the driving force in the world. It could be said that you are Frisk/Chara's DETERMINATION.
  • Set Right What Once Went Wrong: Should you ever have a change of heart during the Genocide route, undoing your mistakes via a Reset is always an option. Once the route has been brought to completion and the entire world has been erased, however, you'll have no choice but to live with your wrongdoing. A complete inverse of this is the player who decides to do a genocide run after fulfilling true pacifist.
  • Superpowered Evil Side: For Frisk, especially when you start killing literally everyone against Frisk's will; remember, Frisk is just a little kid who most likely would not want to hunt down and kill every single monster, and even if they did, being just a child they probably wouldn't have been able even if they tried. You’re the one fighting, the one dodging, and the one killing. In pacifist, you’re a much more benevolent Super-Powered Alter Ego. In a very confusing double wammy, should you interpret Chara's speech as literal, Chara by the Genocide ending could be interpreted to be yours, an embodiment of everything destructive you've ever done in videogames given life by your own hands.
  • Space Time Eater: A sentient time-space anomaly that can consume as many timelines as it wants.
  • Spanner in the Works: The player character can be this, most obviously in a Pacifist Run. Regardless of the run, you undermine each boss' plans to either keep you as a guest or prisoner, kill you, and take your soul to the king or for selfish purposes, or stop you from destroying the world. In fact, once you become friends with everyone, you then undermine Asriel's plan to remake the world and start afresh because you remember each of your friends' likes and dislikes while they are trapped inside Asriel.
  • Stupid Evil: Although there are some interesting things to be found within, like character development, very few people consider the Genocide Route even remotely as enjoyable as the Pacifist route, for a myriad of reasons. It's significantly harder, for example, to the point where the final boss is very clearly designed to be as unfairly frustrating as possible, and the humor and charm is all but nonexistent. As such, many would consider it an unnecessarily exhausting, unsatisfying, and emotionally draining journey to partake in, and Sans, the only character who's aware of your existence, clearly agrees. When analyzing you psychologically at the end of his boss fight, he comes to the conclusion that the only reason you're still here is because you can be.
    Sans: and because you "can"... "have to".
  • Symbiotic Possession: The player controls most of Frisk's actions, but a more benevolent player acts closely to Frisk's desires anyway. As Frisk is a child, they arguably couldn't complete their quest without you, even if they could use determination on their own.
  • Time Master: In this game, resetting and reloading are real, In-universe things.
  • Talk to the Fist: On the Genocide path, you often walk up to the major characters and one-hit-kill them without a word.
  • Technical Pacifist: Possible if your main method of Sparing is to beat the opponent until they have low health, though the fact that monsters take more damage the lower their health is makes this impractical. You can also engage in multiple Kick the Dog moments via dialogue options without having any impact on a True Pacifist run.
  • Tom the Dark Lord: You are most likely going to be this in a Genocide run. Why would your own name be scary?
  • Ultimate Evil: You can become this if you try hard enough. The Fallen will attempt to take this title from you at the end of the first No Mercy run, but if you're cruel enough over subsequent runs, they will eventually give up on out-eviling you. Notably, the Fallen is outright confused at how you could possibly be eviler then them even while admitting it's true. Also true in a more specific sense as, being the player, of course you don't show up in the game.
  • The Unfettered: Undertale is heavy on meta commentary about how your actions can affect the game's world for the worse, what might be your reasons for pursuing bad outcomes, and even how much you're willing to cheat to take what you want from the game. If the worst comes to pass, Sans accuses you of having done it all just because you could and the Fallen Child outright calls you the sort of person who thinks themself to be above consequences and who acts on perverted feelings for the game's setting. You can prove that and assert your power over the game by erasing the records of your deal with the fallen human. On the other hand, there are plenty of people out there who have resisted the temptation of doing a Genocide run and who even hesitate in doing a True Reset after listening to Flowey's last request. However, the game does not spare calling out those who may have been pacifists themselves, but watched someone else take the Genocide route instead.
  • Vile Villain, Saccharine Show: One of three, along with Flowey and the Fallen Child, as you are the one who plays the No Mercy run, which makes you the biggest Knight of Cerebus; interestingly, you have the choice to be the reverse and make the game happy and quirky.
  • Villainous BSoD: A very, very common reaction — the intended reaction, even — for those who play the Genocide route, especially those who had no idea what they were getting into. Some choose to reset and undo their mistakes at that point, while others choose to grit their teeth and press on anyway.
  • Well-Intentioned Extremist: You can invoke this (especially if this isn't your first playthrough) as an excuse to kill every boss monster while sparing the citizens. This results in the Annoying Dog taking over the throne, and arguably the second-best ending in the game right after True Pacifist. Even Sans would say thanks at the end of it, despite him being rightfully angry at you for killing his brother earlier. This can also apply to players who started out sparing the monsters but killed at least a few of the later encounters because they just couldn't find out how or they didn't find them to be worth the effort.
  • What the Hell, Hero?: Beating the game on the True Pacifist Run and rebooting the game gets you a lecture from Flowey of all characters, calling you out on taking the characters' happy ending away from them because you were bored, and referring to you as a possibly worse person than him.
  • Wrong Context Magic: Even if it's only a few people, there are those who know about the power of determination and resetting. What they don't know about is the Anomaly's power to alter the game's data. Even Chara's attempts to trap them with the consequences of the Genocide run are nothing in the face of this.
  • Wrong Genre Savvy:
    • The first boss asks you to prove that you're strong enough to survive outside. Anyone familiar with Role-Playing Games in general would try to beat Toriel to an inch of her life before Sparing her. The encounter's designed so that she's instantly killed when her health reaches 30%, and you're guaranteed to feel like a scumbag afterwards.
      • Interestingly, on a Full Pacifist Route the game does this to you again with Asgore but in reverse. Asgore's boss fight plays the RPG trope straight, you HAVE to fight and beat him within an inch of his life to Spare him but by then you've played almost the entire length of the game having adapted to its new rules. You end up frustrating yourself trying to find a hidden (non-existant) trigger for a non-violent Mercy Condition just as you've done all game for every other monster. Wrong Wrong Genre Savvy?
    • The game itself is very meta, and if you think you can just save and load as you please to see what would happen if you do this or that, you will be in for a nasty surprise.
  • Yandere: You can be a platonic version of this if you reset a True Pacifist ending, taking away a happy ending in order to spend more time with characters you've grown to love.
  • Yank the Dog's Chain: How the aforementioned permanent Heel–Face Door-Slam manifests. Even if you do everything right and get a Pacifist Ending, in the end, the Fallen Child is revealed to still have Frisk's soul, after which they'll take control and possibly starting killing again, anyway.
  • Your Approval Fills Me with Shame: Just like My God, What Have I Done? trope above, the game evokes this trope to the player at its hardest. When Flowey or Chara/the fallen human congratulates you, the player (and/or Frisk) for killing Asgore and/or Flowey himself in the Neutral route on the former, and completing the Genocide/No Mercy route on the latter.

    Asriel Dreemurr
It's me, your best friend.
Absolute GOD of Hyperdeath 
Final Form 

The deceased (and later reincarnated) Crown Prince of the Underground. His mind was resurrected within a flower that had Determination injected into it, but without a SOUL and the ability to feel compassion, he was twisted over time into the being calling itself Flowey.

If you want to see information about Flowey, his reincarnation, visit his page.

  • Abnormal Limb Rotation Range: When using his Chaos Saber attack, he rotates his head 360 degrees, vertically before delivering the last slash.
  • Amazing Technicolor Battlefield: In his powered-up form, he will wait for the music to swell before turning the background into a trippy rainbow tunnel.
  • Animesque: In the final battle, he crosses the Bishōnen Line, gives himself an over-the-top Large Ham Boss Subtitle, calls his attacks, and the attacks themselves are visually stunning and look like complete overkill. It's actually a kind of sad twist on this trope by reminding you that under that almost demonic looking exterior, he's just an eight-year old fighting like how he would have seen in a cartoon or read in a comic.
  • The Anti-Nihilist: In contrast to Flowey, once redeemed, Asriel expresses the opinion that while the world can be a dark place filled with Floweys, what should be strived for is an existence where nobody kills and nobody is killed.
  • Anti-Villain: Really, he is just a child who was betrayed by his adoptive sibling, whom he still loves and misses. He just doesn't want to be alone anymore.
  • Arm Cannon: One set of his attacks in the first stage of his boss fight has him morph one of his arms into a gun.
  • Baleful Polymorph: Alphys' experiments on monster souls and Determination led to him being inadvertently reincarnated as a soulless flower known as "Flowey." In the Genocide route, Flowey recounts how horrifying it was when he awakened to find that he couldn't feel any of his limbs; in the True Pacifist route, when he regains his original form as Asriel, the first thing he does is test his newly-regained arms, silently laugh to himself, and mention how he was so tired of being a flower.
  • Became Their Own Antithesis: The All-Loving Hero who died because he refused to lift a finger in self-defense against his people's ancestral enemy was twisted by forces beyond his control into an Omnicidal Maniac. And when he returns to his old self, he's soon paralyzed by the accumulated guilt his Flowey form had suppressed all those years.
  • Berserker Tears: Once you save the souls of all your closest friends from within him, you are given the opportunity to save him. Soon, he starts to break down. He'll begin to sob while begging you to let him win, that you and he will be happy together, eventually bursting into a bawling scream as he fires a point-blank Death Ray at Frisk.
  • Big Sibling Worship: We don't know if The Fallen was any older than Asriel, but Toriel vaguely admitted that he did great admire The Fallen and took up copying their habits.
  • Bishōnen Line: His final boss form is far more powerful than the boss form he assumed as Flowey in the Neutral run, and is also much more anthropomorphic, simply being a grown up version of himself with slightly demonic features. This ends up getting played with a bit upon his transformation into his final form, which is strange and mechanical-looking, but is still nowhere near the abomination Flowey became.
  • Black Eyes of Evil: In his Bishōnen Line form, his sclerae are black with narrowed white pupils, contrasting both of his parents, who have standard white sclerae and dark pupils.note 
  • Blasting Time: Both of Asriel's Final Boss forms have attacks that involve raising his arms above his head first Justified, as Asriel is still at the maturity level of a child, and is probably copying shows he watched where the characters did this, making it an In-Universe example of Rule of Cool.
  • Boss Subtitles: He's the sole individual who actually has a boss subtitle during his introduction, which makes sense, given that he's a little kid given god-power, and everything he does in this form is his idea of Rule of Cool.
  • Break the Cutie: His circumstances really break him so much. Part of the reason why Flowey is so awful is because he represents Asriel's guilt and despair of being helpless to descalate the conflict that lead to his and the Fallen Child's deaths.
  • Calling Your Attacks: During the first phase of his fight, the text box will announce which attack he'll use (Star Blazing, Shocker Breaker, Chaos Sabers, and Chaos Buster). The same attack types even have upgraded versions with different names he uses halfway through (Galacta Blazing, Shocker Breaker II, Chaos Slicer, and Chaos Blaster). Funnily enough, Asriel isn't actually saying the attacks in his text speech balloons; it's the narrator describing them. This trope still applies, though, because it's clear that at least someone is describing them.
  • Came Back Wrong: As is said early in the game, when a monster's ashes are scattered onto their favorite thing, their essence lives on, permeates it, even without a SOUL. Unfortunately for Alphys, she had no idea that the flower she'd chosen to bring to life through Determination was carrying Asriel within it. Thus, the product was a soulless vessel carrying the will and intelligence of their crown prince, with no capacity for any kind of love: Flowey.
  • The Chosen One: In the True Pacifist route, he becomes the Angel spoken of in the Delta Rune's prophecy; he has seen the surface before, having gone there in his attempt to return Chara's body, and upon returning to his true form and being redeemed, he uses his power to shatter the barrier.
  • Clipped-Wing Angel: He's far less aggressive and 'unfair' than Photoshop Flowey, and despite being far more powerful, his attacks are likely a little easier to deal with (even discounting the player getting permanent Auto-Revive for the fight). This makes perfect sense, really, as absorbing all those love-filled souls restored his conscience, and he's clearly struggling to sustain the hatred powering his attacks.
  • Crucified Hero Shot: After you save him and get him down to his normal child form, he releases the souls of the monsters and the Fallen Children this way. This also shatters the barrier.
  • Determinator: Manages to force control from Chara and run away from the humans, even while being murdered. As a reminder, Chara is a borderline eldritch abomination who usurps the player (aka God) in the No Mercy run.
  • Even Bad Men Love Their Mamas: His base-power form is borrowed from Toriel's appearance — same height and width, though he wears a tabard with the Delta Rune on it, and has horns that curl outward, as well as the aforementioned Black Eyes of Evil.
  • Even Evil Has Loved Ones: It's the driving force behind his villainy. He simply cannot let go of the Fallen Child.
  • Fallen Hero: In life, he was selfless enough to choose death over murder. After his reincarnation, he'd come to regret his sacrifice and, as a result, adopt a worldview antithetical to it.
  • Fallen Princess: Gender-flipped. As shown to Flowey's entry, a bad combination of brutal death, botched up resurrection, boredom, and grief eventually twisted this poor monster.
  • Fate Worse than Death: No matter what choices you make, you can't save Asriel and bring him to the surface with you. He is either stuck in the underground as Flowey for the rest of his reincarnated life in a True Pacifist run with no one other than Frisk knowing that he was ever brought back, or has that vessel mercilessly hacked to pieces in a Genocide run (presumably, either Cessation of Existence or And I Must Scream apply for the latter).
  • Fighting from the Inside: Tragically, while this doesn't happen when he's Flowey, when spoken to in the True Pacifist's epilogue he states that the Fallen Child wanted to use their combined power to annihilate the humans living in their hometown (probably to defend themselves). Asriel resisted, and they were mortally wounded as a result.
  • Final-Exam Boss: Rescuing the Lost Souls involves fighting them in the Red (Toriel and Asgore), Yellow (Dr. Alphys), Green (Undyne), and Blue (Sans and Papyrus) heart modes.
  • Final First Hug: With Frisk, if the player chooses to comfort him at the end of the Pacifist Run.
    Asriel: Ha... ha... I don't want to let go.
  • Foil: As a boss, he's one to Sans, who's fought at the end of the polar opposite route of the one that Asriel is found in. Despite being labeled as having infinite ATK and DEF, Asriel's attacks aren't too difficult and only deal a finite amount of damage, plus you literally can't lose. Sans, on the other hand, is claimed to be "the easiest enemy", and despite having only 1 Attack and 1 Defense, he packs brutally hard attacks intended to wreck you in the most unfair ways possible. You fight Asriel to get back all the souls he absorbed and automatically revive when killed out of sheer determination to save them, while Sans fights you to protect what's left of monsterkind by kicking your ass until you give up. Story-wise, he tries to manipulate you into a "kill-or-be-killed" mentality as Flowey, while Sans tries to befriend you to prevent such a thing from happening.
  • Godhood Seeker: His ultimate plan, both as Flowey in the Neutral route, and as his resurrected self in the True Pacifist route. He thinks he and Chara will become gods in the Genocide route as well. He's wrong.
  • Grand Theft Me: A victim. Asriel absorbs Chara's soul in the backstory, acquiring a new powerful body, but much to his horror, finds out that Chara also has control over that body and wants to attack the people of their home village with their newfound power. It takes every ounce of willpower to resist the Fallen Child's will.
  • The Greatest Story Never Told: At no point in a Pacifist Run (the only run where Asriel can actually come into being) can he be reunited with his parents, or even have the fact he exists again be known to any other character. After he redeems himself, he purposely puts himself out of sight from anyone who knew him, knowing the joy of reuniting with his loved ones would be tragically short-lived, given that he still lacks his own soul and will eventually revert back to a souless flower.
  • Heel–Face Turn: Asriel pulls this at the end of the True Ending, having regained his ability to feel compassion (at least temporarily).
  • Heel Realization: Asriel during his boss fight with you, when you reawaken the monster souls he has absorbed and he starts to regain his compassion. After he turns back into Flowey, he uses this trope as the reason why the player should erase his memories too, should they decide to start a new game — he feels so bad about how terrible he was to everyone around him that he doesn't think he'd be able to play the same role again.
  • Hoist by His Own Petard: Throughout the game, especially in a Pacifist run, he repeatedly exploits the trust and compassion of the people around him in order to get all monster and human souls in one room and devour them simultaneously. When he finally does, he gains the power of a god — but also regains his own compassion, and Frisk's pacifism turns him from a sociopathic maniac to a sobbing wreck who can't bring himself to hurt people anymore. And if you do the True Reset, he points out you're even worse than he is because you're enacting the very same insane, evil plan he was trying to do after even he himself had let it go.
  • Horrible Judge of Character: The Fallen Child claiming that they hate humanity, all the info they give about their past and the reason for climbing the mountain being only a vague and cryptic "unhappy reason" and then planning a suicide mission against their own kind should've raised some red flags for Asriel.
  • Hopeless Boss Fight: Just like when you face him as Flowey, he tries several times to convince Frisk that they are completely helpless. In actuality, Frisk is this for Asriel. No matter what Asriel does, or how many times Frisk is brought down to 0 HP, Frisk's determination keeps them going.
  • HP to 1: His final beam attack will reduce your life meter to 0.0000000001/20 HP — one ten-billionth of a hit point. Subverted, however. That's not what it's intended to do. It's supposed to kill. Frisk is just that determined to stay alive.
    • If you get hit by his powered-up form's final attack, the Hyper Goner, you instantly drop to 1 HP.
  • I Hate Past Me: In the epilogue of the True Pacifist playthrough, he expresses sincere remorse for his actions as Flowey, to the point where he asks Frisk to consider his two forms to be separate individuals should they meet again after he's reverted to being Flowey.
    Asriel: Let's be honest. I did some weird stuff as a flower.
  • I Just Want to Have Friends: The Fallen Child was the closest thing Asriel had to a friend, with the monsters suggesting that Asriel and the Fallen Child were like siblings. Asriel simply cannot let go of his memories of them, to the point of projecting the Fallen Child onto Frisk; he just wants to see his friend/sibling again that badly. This is part of why his Flowey persona is so elated to see the similarities between the two at the start of a Genocide route.
  • In-Universe Catharsis: Asriel experiences this at the end of the True Pacifist route. Part of his jaded views as Flowey stemmed from the fact that he blamed himself for his and Chara's deaths and their plan failing, since his Fighting from the Inside to prevent Chara from killing the human villagers led to the humans killing them instead due to a misunderstanding. At the end of the game, Asriel is finally able to let go of his guilt and regret after meeting Frisk makes him realize that Chara wasn't as great of a person as Asriel had been trying to convince himself they were, and that he did the right thing by preventing Chara from killing them.
  • It's All My Fault: He explains that his "Kill or be Killed" outlook as Flowey came from him blaming himself for preventing the Fallen Child from attacking the humans, which resulted in them dying and Asriel being reborn as a flower. His jaded belief that "love and compassion" only cause pain and suffering is due to this as well, as he refuses to believe that his beloved Chara is at fault and blames his decision to spare the human village instead, as the cause of everything that came after and the pain he and his loved ones experienced because of it. Luckily, he finally gets over this at the end of the True Pacifist run, realizing that he did the right thing and accepting that Chara "wasn't really the best person".
  • Large Ham Title: After the music swells, the "Check" command declares Asriel "The Absolute GOD of Hyperdeath!"
  • Leitmotif: Your Best Friend and Memory, which is further reprised in Undertale and His Theme. For his boss fight, he gets Hopes and Dreams, Burn in Despair!, and SAVE the World, in that order.
  • Light Is Not Good: His hyperdeath form looks like an angel and has rainbow light attacks.
  • Like Father, Like Son: There is at least some hints of it. Most notably in how he names himself "Flowey the Flower" after having been reincarnated as said flower. He clearly has inherited his father's penchant for coming up with lame names.
  • Living on Borrowed Time: In the Playable Epilogue of the True Pacifist, he's restored to his true form, but says that without a soul, he'll eventually return to being Flowey.
  • Luke, You Are My Father: Odd example. Neither Toriel nor Asgore find out that Flowey is Asriel, but Frisk does.
  • Many Spirits Inside of One: His final form, comprised of every soul in the underworld.
  • Meaningful Echo: After you go back to the first screen of the game and talk to him, he'll end the conversation with "Don't you have anything better to do?"
  • Meaningful Name: His name is chock-full of meaning:
    • Asriel's name shares the Theme Naming of angels and means 'Prince of God' in Hebrew, or 'One who helps God'. Fitting for someone who will be the key of freeing his people from the Underground.
    • "Asriel" is an amalgamation of Asgore and Toriel. As mentioned before, Asgore is really bad at naming things.
    • If you rearrange the letters in "Asriel Dreemurr", you get "Serial Murderer". Doubles as an Ironic Name for Asriel, but plays straight in his later life as Flowey.
  • Morality Pet: It's pretty clear that whatever Chara was really like, they had some level of fondness for Asriel, possibly at the exclusion of everyone else. Whether this fondness was shallow and ultimately unimportant to them in the grand scheme of things, genuinely deep and familial, or anywhere in between is still hotly up for debate.
  • Morphic Resonance: Flowey and Asriel share the exact same color pallet: green, yellow, white, and black. Asriel has a fifth color in his overworld sprite, purple, but otherwise uses the exact same colors. Also, at the end of the Genocide route, Flowey reveals that he can still mimick Asriel's real face and voice, whipping them out only as a last ditch attempt to stop the player from killing him, which still fails.
  • Names To Run Away From Very Fast:
    • Asriel is also a reference to Azrael, the name of the Archangel of Death. In one of his forms, Azrael has four faces and four thousand wings, and his whole body consists of eyes and tongues; the number thereof corresponds to the number of people inhabiting the Earth. Sound familiar?. He will be the last to die, recording and erasing, constantly in a large book the names of men at birth and death, respectively, paralleling his control of the game overs as Flowey. His name is also an anagram that spells Serial Murderer.
    • The Absolute GOD of Hyperdeath is something that Asriel (and the narrator) calls himself during his fight.
  • Nigh-Invulnerable: You cannot harm him in the final battle. Asriel becomes everything the human ancestors feared. Thank goodness, like all monsters, he regains his love and compassion, or else you'd be screwed.
  • No Good Deed Goes Unpunished: All he wanted to do was return the Fallen Child's body to their village out of respect. The humans thought he killed the Fallen Child, and attacked him, leading to his own death.
  • Non-Standard Character Design: During the fight against Asriel, the screen suddenly starts displaying rainbow patterns in the background, and his name is listed in dancing rainbow text in the ACT menu.
  • Older Alter Ego: When he fights you, he ages himself up from a child to what looks to be a young adult. He reverts back to his child form once he loses the will to fight, though he briefly assumes his older form again for a gag during the True Pacifist credits.
  • One-Winged Angel: After absorbing the Fallen's SOUL, Asriel was stated to have undergone a transformation into a powerful form, which is presumably the same form he takes during the first stage of his boss fight and simply resembles an adult version of his species, similar to his parents. His final form also qualifies, as it resembles a winged, demonic version of himself.
  • Only Friend: Chara. The entire reason he's putting Frisk through a fight is because he thinks they are Chara, and if the player gets their "happy ending", "Chara" will leave him forever. Whether his fears are founded depends on if the player subscribes to the "Chara is the Narrator All Along" theory or if they've cleared a Genocide route previously, though the second case could be a blessing in disguise...
  • Our Ghosts Are Different: Unlike the Blook family, Asriel is dead and only persists due to having been accidentally revived as Flowey. Once he collects all the SOULs in the Underground, he gains enough power to recreate himself, but chooses to restore everyone instead.
  • Overly Long Gag: If you exhaust conversation with Asriel in the Playable Epilogue, you get this:
  • Physical God: In his Boss Monster form, he not only has the power of six human SOULs, but of all the other monsters the Child has encountered except Napstablook, making him even more powerful than Photoshop Flowey.
  • Platonic Declaration of Love: While the word "love" is not used, this is how his boss fight ends. Asriel starts by saying the player (who he's projecting his feelings about Chara onto) is special and the only one who is still fun to play with, but then isn't satisfied until he adds how much he genuinely cares about them.
  • Playing with Fire: One of his attacks, shared with both his parents, is a storm of fireballs. Also, like his mother, towards the end of the fight, the fireballs will intentionally start avoiding the player's SOUL.
  • Please Don't Leave Me: Said almost verbatim during the final fight against him on the pacifist route and combines this with Berserker Tears.
  • Portmanteau: Asgore + Toriel = Asriel. Asgore really is bad at naming things.
  • Post-Final Boss: The Pacifist route's final battle, Asriel Dreemurr, is impossible to lose since you revive each time you die, and you can "dream" for as many healing items as needed. His fight serves less as one final challenge and more as an interactive cutscene which ends the game's story on a high note.
  • Power-Upgrading Deformation: The Pacifist final boss goes from flower to formerly-dead little boy into something made of edge but still recognizable, ending up as half-abstract goat-machine abomination.
  • Prone to Tears: Particularly in his child form.
    Asriel: I always was a crybaby, wasn't I, Chara?
  • Redemption Equals Death: A downplayed example. He considers Flowey to be a completely different being, so by releasing all the souls to destroy the barrier, he knowingly goes through Death of Personality.
  • Reincarnation: After an unknown length of time passes after his death, Alphys's experiments with determination brought him back to life in Flowey's form.
  • Ridiculously Cute Critter: His original child form is this to many fans of the game.
  • Rule of Cool: The form he takes in his adult form during his boss battle is this to a T; his attacks and his appearance all incorporate things he really loves—stars, prismatic color schemes, and (as mentioned before) his mom. Deep down, he's still just a little boy with a big heart, who just wants to be with his best friend and family again. *Sniff*.
  • Sad Battle Music: While you save him more than you fight him, the battle against Asriel ends on the triumphant but dramatic "His Theme".
  • Significant Anagram: His name is an anagram of "Serial Murderer", of all things. Not so appropriate for Asriel himself, but it fits Flowey to a T.
  • Slap-on-the-Wrist Nuke: Asriel Dreemurr has "Hyper Goner" for the ultimate attack of his powered-up form, where the dodging space expands to cover the entire screen (including the status bar). He forms a black hole that sucks you and several damaging diamond shaped projectiles in towards it. Despite the incredible animation, it can only leave you at 1 HP. After that, he transforms into his final form, where you're unable to use items at first and you're forced to dodge several tricky volleys of projectiles.
  • Spanner in the Works: In the backstory, Asriel in the Fallen Child's Thanatos Gambit. The plan was to go above after Asriel absorbed the Fallen's soul, collect at least six more human souls, and free everyone Underground. When humans attacked with Asriel being Mistaken for Murderer for holding his sibling's human body, Asriel refused to lash out. Instead, a wounded Asriel returned to the Underground and died from his injuries, accomplishing nothing.
  • Suddenly SHOUTING!: If you take his Boss Subtitles as this, especially the way the letters shake and leave afterimages on being spelled out.
    Asriel: It's me...your best friend...
  • Suicide by Cop: Unintentional, but Asriel purposely held back his power and the Fallen Child's influence when the latter went to attack their hometown. The humans merely saw a monster carrying the Fallen's corpse and believed they were avenging them by slaying the monster — Asriel accepted this fate rather than let the Fallen annihilate them and possibly kickstart another war.
  • Superpowered Evil Side: Asriel has no powers by himself, but he is nearly godlike when he is reincarnated as a murderous flower and also when he absorbs the souls of the Underground to become the Absolute GOD of Hyperdeath.
  • Tender Tears: Even admits that he's "a bit of a crybaby."
  • That Man Is Dead: Invokes it on himself to Frisk, claiming Flowey is so different that he's someone else.
  • Thou Shalt Not Kill: Played With. In the past, he refused to kill humans; in the present, while fighting him, he tries while attempting to do an infinite "game" with you, but your soul "refused" and will not die.
  • Time Crash: Seeks to cause one after another using the power of the Six Human SOULs along with every Monster SOUL — locking Frisk in an eternal loop of life with him so he'll never have to let them go.
  • Tragic Villain: He clung desperately to the memory of the Fallen Child, and was Forced into Evil as a result of his soulless reincarnation. He has suffered more than any other character, and despite all of Frisk's determination, you can't save him.
  • True Final Boss: Of the True Pacifist ending, which requires having gotten the Neutral-Pacifist ending. Interestingly, he's both a Climax Boss and a Zero-Effort Boss, since you can't lose.
  • Turn Out Like His Father: Inverted. In his powered-up form, he resembles his mother, more than his father.
  • Used to Be a Sweet Kid: Every indication from the story is that Asriel was just as kind as his parents, if not more so. Things quickly went downhill following his friendship with the Fallen Child, the subsequent Demonic Possession, and finally his reconstruction as Flowey without a soul. Getting killed because he refused to fight back and coming back unable to feel love twisted him into something totally unrecognizable from his former self.
  • Victory Is Boring: After his reincarnation and acquiring the power to "save", he actually did a lot of good deeds throughout the Underground, achieving the "best ending" possible. But lacking his love and emotions, found it was all hollow and pointless. He started going down evil paths to see if that would give him any satisfaction — only to brick-wall against fighting Sans.
  • Villain Respect: Being able to stay alive after being attacked by barrage after barrage of his god-like power makes him admit that Frisk really is "something special."
  • Voice Grunting: He uses a much higher-pitched version of Toriel and Asgore's Voice Grunting. It becomes deeper in his God of Hyperdeath form.
  • Wise Beyond Their Years: Asriel is pretty well-spoken in his child form, probably due to how many times he's reset the world as Flowey; despite not much time actually passing for the world, Asriel/Flowey himself has had a very long time to learn about things beyond his age.
  • Wishful Projection: Similarly during his time as Flowey, Asriel believes Frisk is the Fallen Child reborn, the difference is he finally loses the delusion upon his final defeat. Whether he's mistaken or not depends on if you did the Genocide route before the Pacifist route — if you did, the Fallen really is along for the ride, but Asriel doesn't really know this... which might be for the better, since that Fallen Child has long since stopped being the human Asriel knew.
  • Yandere: Just like his Flowey persona and for the same reasons, his desire to keep Frisk (who he thinks is Chara) in the Underground is a platonic variant. Unlike Flowey however, he grows out of it when he finally comes to his senses since unlike Flowey, Asriel is at least capable of empathy and introspection.
  • Zero-Effort Boss: The True Final Boss Asriel. While his attacks aren't easy to dodge, you automatically revive each time you die, and thus the battle keeps going until you win. While dying can prolong the battle, you ultimately can't lose. And his penultimate attack actively avoids harming you, being the exact same as Toriel's.

    The Fallen Child/"Playername"/Chara 
Has their own page here.

    Dr. W.D. Gaster
The "Mysteryman" sprite commonly believed to be Gaster.

The man who speaks in hands. Dr. W.D. Gaster was the original royal scientist, before Dr. Alphys. Can't find him? Well, he didn't exist in the game at all for a while. Originally, if one were to explore the game's files, they'd come across a few odd NPCs, rooms, and messages that were cut. If a player decided to insert these aspects back into the game, what followed was the mysterious tale of a brilliant mind who invented a machine that accidentally caused him to be shattered across reality, with his fate uncertain. Even to this day, no one knows the complete story of W.D. Gaster... well, no one that wants to talk, anyway.

And note that the above instructions on how to activate him are in past tense because now you can access these previously cut elements randomly in the game without having to alter your game. A second Goner was also added in the Switch port, and a figure implied to be very close to him facilitated the reveal of Undertale's successor, Deltarune, with the game itself having a notable amount of nods to the mysterious scientist. As for what this means, however...

  • Ambiguously Evil: Gaster is certainly an ominous figure (see The Dreaded down below), and he looks creepy, but he doesn't actually do anything to suggest he's malicious. Due to just how unknown he is, its really impossible to discern his true nature or what, if any, plans he might have. He might be a bad guy, he might not. Then again...
    River Person: Beware of the man who speaks in hands.
  • Ambiguously Related:
    • To the mysterious voice who unveiled Deltarune to the internet. While their manners of speech are near-identical, and the voice pointedly states that it thought we would find Deltarune "VERY, VERY INTERESTING," no official statement has been made.
    • To Sans, thanks to his Gasterblasters and scientific interests, with this often extending to Papyrus via proxy. Most fanworks depict him as either their third brother or creator/father, but the game is vague about their supposed relationship.
  • Ambiguous Situation:
    • Gaster's life was cut short, and he fell into his creation. But the followers never made clear if it was an accidental death because his experiment went wrong, or one on purpose after his experiment went wrong. One of the followers wonder if Alphys will end up the same way, which may be about her suicide in multiple neutral endings. This isn't even bringing up the possibility that he was pushed into the machine.
      • It's also not specified which 'creation' he fell into. The most likely candidate is probably the CORE, since it's his only confirmed invention - but it's also unclear how a geothermal-powered magical electricity engine causes one to be scattered through time and space, unless there is some detail about it's operation we just don't know yet. Other candidates for his 'creation' include the Determination Extraction Machine (found in Alphys' True Lab but it's implied that she might have not been the one to design it) and the mysterious machine in Sans' secret room.
    • Although some go with the interpretation that he was made to literally have never existed, another interpretation of his fate is that people remember him, but simply don't talk about him anymore. Neither one has been confirmed or denied.
    • It is unknown if the Riverperson warning us about "the man who came from the other world" refers to Gaster. It could refer to Bonus Boss So Sorry due to his theme being named "wrong world", but if its talking about Gaster, what does it the mean that he came from the other world? Is this "world" related to Sans "I gave up trying to go back a long time ago", or just a way of talking about him shattered accross time and space? There is no answer to these questions.
  • And I Must Scream: You can find fragments of him through the world lamenting his horrible fate.
  • Beyond the Impossible: His report mentions negative photon readings, which is a physical impossibility.
  • Body Horror: One of the NPCs who speaks of him is holding a miniature of his head, and his Mysteryman fragment has two gashes on his face - one blinding his left eye, the other cutting into his mouth.
  • Dem Bones: The font Theme Naming convention he shares with Sans and Papyrus, as well as the appearance of the Mysteryman, heavily suggest that he is/was a skeleton monster.
  • The Dreaded: Along with his status as a once powerful scientist, he has many associations with the number 6, meta game mechanics, Determination, and general warnings to be wary of or avoid even speaking of him. Whoever Gaster was, it's possible he was, or is now, very dangerous. "Beware of the man who speaks in hands."
  • Dummied Out: An examination of the horrors of this trope. Gaster is lost through the game's files, unable to interact with anyone and aware that life goes on without him as if he's never existed. Players can search for him, but there's no way to help and so they can only wonder What Could Have Been if Gaster wasn't so unfortunate to be a cut character. A patch later made it so the Fun events work without needing to capitalize "fun" in the save file, but there're no new ways to interact with him yet. In addition, it seems that Gaster is very closely related to Grandpa Semi, a cut character whom little is known about.
  • Eldritch Abomination: He exists, yet he doesn't.
  • Expy:
    • The mysteryman sprite is modeled after Uboa. Just like Uboa, there's a hidden RNG dictating whether or not it'll show up.
    • Being a scientist stuck in a prison of his own making is similar to Dr. Andonuts in Toby Fox's The Halloween Hack.
  • Failure Is the Only Option: In a currently deleted tweet, Toby stated that "You've all seen the happiest outcome. Neither of them could fix the machine, no matter how hard they tried. No one can."
  • Foil: In a sense, Gaster is very much an opposite of the Fallen Child.
    • They are both surrounded by an aura of mystery and vagueness, with very little known about them beyond what they offered to the underground. Chara provided them with hope, while Gaster provided the Core and presumably other creations.
    • The Fallen Child somehow ended up with Frisk and could be the greatest evil depending on the player's choice, and the story of Undertale resolves about the relationship of Chara and Asriel; Gaster simply vanished and his tale is not touched upon unless the player tempers with the game files, with only very few people remembering him: The Riverperson and presumably Sans.
    • The Fallen Child is remembered fondly by the Underground, with all of monsterkind lamenting their death alongside Asriel's. Gaster is feared, with the Riverperson telling us to "beware of the man who speaks in hands".
    • Lastly, Chara was a normal human child before their death. Gaster was a genius monster before his life was cut short. They both became something else.
  • The Ghost: His existence is only vaguely hinted at through the game. Dr. Gaster was the previous royal scientist before Alphys, but his experiments have gotten him shattered across the time-space continuum. His predicament is so bad that players originally learned about him by fixing a "typo" in the game's save file (Changing the "fun" item to "Fun" and setting it to certain values. After a patch, changing it became unnecessary.) and then trying to puzzle it out through data mining and trial and error.
  • Ghostly Gape: One of his fragment (serving as his folder's image) looks like it might be a skeleton like Sans and Papyrus, but with that particular expression and the cracks on his face, it ends up looking more like a ghost. Given his predicament, it's probably fitting.
  • Glitch Entity: His existence is an exploration of this trope, and what such a character would be like within the context of the game world itself.
  • Gone Horribly Right: It's a common headcanon that his machine was created to solve the problem of the Barrier, but whatever timespace shenanigans it would have used to remove it ended up affecting him instead.
  • Gone Horribly Wrong: As brilliant as he was, his life was cut short; one day, his experiments went wrong, he fell into his own creation, and... poof.
  • Hoist by His Own Petard: Non-villainous version. Gaster was the one who designed and built the Core, providing the Underground with electricity. Unfortunately, an accident caused him to plummet into one of his creations - presumably either the Core or Sans' broken machine - the damage of which was so severe that it blasted him and possibly some of his colleagues across time and space.
  • It's a Wonderful Plot: For poor Dr. Gaster, this trope appears to have gone horribly wrong; one of his grey fragments asks the player about the prospect of a world where everything is exactly the same except you don't exist, everything functioning perfectly without you. What's worse is that he wasn't erased from history, and yet life still went on; one might assume that nobody mourned. And it even seems to be worse than that. Other NPCs needed to be coded back into the game to get any information on him. Whatever happened was so bad it did the same to anyone who knew much about him... except for one being: Sans, who wields weapons named after him, is implied to have researched a supposed anomaly messing with timelines alongside him, and may or may not be related to him in some way or another.
  • Leitmotif: "Gaster's Theme", a song that can only be heard in a secret Sound Test screen that only features a few apparently unused songs and locks up once the player gives "feedback" by listening to it. Fittingly enough, the vessel survey that opens Deltarune plays a remix of his theme.
  • Meaningful Name: Named after the Wingdings font, which he uses to speak and write. Much like the man himself, Wingdings is cryptic and mysterious, and it takes a lot of effort to memorize and understand. "Gaster" probably comes from the Old English word "gast," from which the word "ghost" derives. "Aster" is also the name of a typeface and is a genus of flowers. In the game, Sans snores in Zs that look close to the Aster font instead of the usual Comic Sans, but that only raises more questions.
  • Morally Ambiguous Doctorate: He's a rather ominous doctor, between his dangerous creations and the fear of those NPCs which discuss him.
  • Number of the Beast: There is data in the game for a possible battle encounter against Gaster. For some reason or other, his attributes have the number 6 in every digit. 66 being the Fun value that specifically reveals the door to Mysteryman's room at Waterfall is one factor that plays into fans assuming he is what Gaster looks like.
  • The Omnipresent: He's been scattered across space and time. And he seems to be able to eavesdrop on everything.
  • Painting the Fourth Wall: Initially it was necessary for players to make a quick fix to the game's save file to enable the content related to Gaster. After a number of patches and ports this content was made available by default and expanded. The announcement of Deltarune was later made by an unknown entity who remarks they and the audience have been looking for each other for a while, and that they look foward to connect with them.
  • Production Foreshadowing:
    • His existence in Undertale supposedly is meant to foreshadow the existence of Deltarune. The secret room 272 with the mysterious figure that says "redacted" in wingdings leads to a Sound Test, and the moment you put Gaster's theme, it will say "thank you for your feedback! Be seeing you soon!", which lead to Deltarune supposed connection with a mysterious voice who was waiting for us.
    • The original version of Deltarune's website in December 2015, unnoticed by the entire player base back then, was a pitch-black page with a hidden message in Wingdings:
  • The Professor: A tall skeleton(?) with a goofy grin who speaks entirely in Wingdings. Also the most brilliant mind in all of monsterkind.
  • Ret-Gone: Apparently, whatever fate befell Gaster took his history with it, as even learning his name requires extreme luck and/or messing with the code.
  • Riddle for the Ages: While there are some "models" of Gaster that are more popular in fanon interpretation, at the end of the day, he as a character is an absolute mystery on just about every level. We have no idea what he was like as a person, what his goals or relationships were, or even his exact fate and how it befell him; all that is known for certain about him is his former role as the royal scientist, the fact that he no longer properly exists and likely never will again, and the fact that he has some kind of important connection with Sans.
  • Tempting Fate: One of the grey NPCs that explains the story behind Gaster says he has nothing to fear from him, since he has a piece of him. He vanishes immediately after he's done talking. A notable case because none of the other grey NPCs disappear until you leave their rooms... and because his disappearance is accompanied by the exact same sound that plays when Gaster himself (or, at least, whatever apparition serves as his image shown above) vanishes, too.
  • Tough Act to Follow: In-Universe. One of his followers says that after Dr. Gaster's death, the Royal Scientist position stayed empty for so long because nobody could follow Gaster's act.
  • The Unintelligible: Like Sans and Papyrus, Gaster speaks in the font he is named after - in this case, Wingdings, which... probably isn't a "dialect" the player will understand. Fortunately, lots of translation tools exist online.
  • The Unreveal: It's never explicitly stated which of Gaster's creations caused him to become scattered across space and time. Possible canditates are the CORE, the Determination Extractornote  and the mysterious machine hidden in Sans' basement.
  • Vagueness Is Coming: Among Alphys' reports, there is the elusive Entry #17 in which Gaster talks about doing research on an ever expanding darkness. He then asks what two unknown people think about it.
  • Voice Grunting: The oddest sounding variety of it in the game: a jumble of random text-to-speech programs speaking in gibberish, only heard in the hidden Entry #17. They're actually fragments of a text-to-speech message from Toby Fox asking players not to spoil the game's secrets. The "Version 1.01" patch replaced the message with a bunch of text-to-speech voices laughing, one after the other, which sounds pretty much the same when jumbled up.
  • Wham Line: His followers all speak of Gaster in the past tense, and the snippets of his story you hear all imply that he's dead, gone, or Ret Goned. That is, until you speak to follower #3, whose final line suggests something much stranger:
    "Well, I needn't gossip. After all, it's rude to talk about someone who's listening."
    • Similarly, there's the final line of Entry #17, which implies...well, it implies something, alright:
      "...what do you two think?"

    Gaster's Followers and Goners 

"However, his life... was cut short."

A group of characters that are all related to the game's internal "Fun" value, there are five characters total: Gaster Followers 1-3, "Goner Kid" and Goner Clam Girl. The former three directly talk about W.D. Gaster himself, and while the latter two never talk about Gaster directly, they're usually lumped together with the other three for the sake of simplicity (and they can only appear at a certain Fun value). What's notable about these characters as well is that, if the player leaves the room that they appear in, they will always disappear. Except for Gaster Follower 2 and Goner Clam Girl, who literally disappear right in front of the player's eyes after finishing their sentence.

Tropes that apply in general

  • Ambiguous Gender: With the exception of Goner Clam Girl, they are never given a canon gender. Most players assume "Goner Kid" is female because of how it looks like it's wearing a bow, compared to Monster Kid's having horns.
  • And I Must Scream: Like Gaster, none of them appear in the game itself without altering the game's coding until the 1.0.1 patch, where they can appear randomly.
  • Deliberately Monochrome: All five of them are grey.
  • The Last of These Is Not Like the Others:
    • Unlike the rest of the followers, Gaster Follower 3 is not a Palette Swap of an already existing NPC. However, it receives a "normal" counterpart in Deltarune, portrayed as a hunched-over bird.
    • The Clam Girl transforms into her goner counterpart, rather than existing separately from her.
  • No Name Given: None of them have received names.
  • Palette Swap: Gaster Followers 1-2, "Goner Kid" and Goner Clam Girl are all palette swaps of several of the preexisting monster characters. Notable in that, despite being palette swaps, they all have notable differences from the "normal" versions.
    • "Goner Kid" = Monster Kid
    • Gaster Follower 1 = The ficus licker in MTT Resort
    • Gaster Follower 2 = The monster holding the donut at the Spider Bake Sale
    • Goner Clam Girl = The Clam Girl near Napstablook's house
    • Gaster Follower 3 also turns out to be a palette swap. ...of an NPC who appears during the Playable Epilogue of the sequel. You can find them in the library while walking around the town.

Tropes that apply to Gaster Followers

  • Body Horror: Follower 3's normal appearance is revealed in Deltarune, but given their differences it seems as if the follower has lost their lower jaw, had their throat cut and their feet melted into the floor.
  • Mr. Exposition: All three of the Gaster Followers only talk about what happened to W.D. Gaster in some form.
  • Oracular Head: The "head" in Gaster Follower 2's hand is the one talking.
  • Properly Paranoid: Gaster Follower 3 believes it'd be "rude to talk about someone who's listening" in regards to Gaster. It might not be paranoia given that Gaster Follower 2 holds "a piece of" Gaster.
  • Rhymes on a Dime: Gaster Follower 2 does this if you look closely.
    Gaster Follower 2: Alphys might work faster. But the old Royal Scientist, Doctor W.D. Gaster?
    One day, he vanished without a trace.
    They say he shattered across time and space.
    Ha Ha... how can I say so without fear?
    I'm holding a piece of him right here.
  • Satellite Character: To Dr. Gaster, as they are only there to provide information about him. They might also be the persons pictured on the photographs in Sans' basement, but that is just speculation.

Tropes that apply to Goners

  • Connected All Along: The Switch version reveals that the Clam Girl can transform into her goner counterpart, suggesting that she has some connection to "Goner Kid."
  • The Ghost: Suzy, the Clam Girl's neighbor's daughter. As of the Switch update, the Clam Girl hints you might meet her soon. This is seemingly Production Foreshadowing for Deltarune, where Susie appears as a deutoragonist.
  • Monochromatic Eyes: "Goner Kid" has completely blank eyes.
  • Surprise Creepy: The Clam Girl, when she transforms into her goner counterpart, appears with a single, bloodshot eye in place of her head.
  • Tomato Surprise: As of the Switch update, the Clam Girl transforms into her goner counterpart, if you find her after a Pacifist run.
    Clam Girl: So you never met my neighbor's daughter.note 
    But please don't despair.
    Because the time that you will meet her...
    [Music stops.]
    * ... is fast approaching.note 
  • Unknown Character: The Clam Girl's neighbor and the parent (Gender is never specified) of Suzy. No information is about them has been revealed, for all we know they could be just an Invented Individual. We do meet Susie in Deltarune, but we haven't gotten any information on Susie's family yet.


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