Long ago, humans and monsters went to war. The humans won and sealed the monsters underground behind a magic barrier. Undertale begins when a human child climbs Mount Ebott, falls into the Underground, and has to find a way home. Every monster you meet will try to fight you. You can fight back, or you can talk, joke, flirt, pet and comfort your way through every encounter without hurting anyone.
That choice is the heart of Undertale, and it changes not just how fights end but who these characters become. Released in 2015 and made almost entirely by Toby Fox, it's one of the most beloved indie games ever made, largely because of its cast. This guide introduces them roughly in the order you'll meet them, then covers the bosses, the minor monsters and the routes. The cards avoid major twists; anything that would spoil a first playthrough is collected in marked sections.
- Creator
- Toby Fox
- Released
- September 2015 (PC), later on consoles
- Genre
- Role-playing game with bullet-hell battles
- Additional art
- Temmie Chang
- Routes
- Neutral, True Pacifist, Genocide
- Companion game
- Deltarune
The main cast
Undertale's main characters are a small group of monsters who, on a peaceful run, become your friends. Each one also has a very different side depending on how you play.
Frisk
The fallen human · Player character
The child you control is a quiet, striped-shirted kid with no lines of their own. Their actions are entirely yours, which is the point: the game is about what you choose to do with them. Frisk is deliberately ambiguous in age and gender, and most players refer to them as "they." Their real name is only revealed at the very end of the True Pacifist route.
Flowey
The flower · Antagonist
Flowey is a smiling golden flower who welcomes you to the Underground, offers to teach you how things work, and then tries to kill you. He explains the world's philosophy in a single brutal line: in this world, it's kill or be killed. He reappears throughout the game, watching, mocking and sometimes knowing more than he should about your previous saves.
Toriel
Caretaker of the Ruins · Boss monster
Toriel is a gentle goat-like monster who rescues you from Flowey and takes you home to her house in the Ruins. She bakes butterscotch-cinnamon pie, tells terrible jokes and wants you to stay with her forever, where it's safe. When you insist on leaving, she blocks your way. Her fight is the game's first test of whether you'll find another way, and many first-time players never forget it.
Sans
Lazy skeleton · Sentry
Sans is a short skeleton in a blue hoodie who's supposed to be on lookout for humans but would much rather tell jokes, nap and sell hot dogs. He's friendly, relaxed and clearly more aware of what's going on than he admits. On a peaceful run he's one of your best friends. On the darkest route he becomes something else entirely, and his fight is the most famous in the game.
Papyrus
The Great Papyrus · Aspiring Royal Guard
Papyrus is Sans's tall, loud brother, who desperately wants to capture a human so he can join the Royal Guard and be popular. He sets elaborate puzzles that he then explains to you, cooks a lot of spaghetti, and believes the best of everyone, including you. He's possibly the kindest character in the game, and it's very hard to dislike him.
Undyne
Captain of the Royal Guard
Undyne is a fiery fish-woman with an eyepatch, a spear and a passionate belief that she's the Underground's hero. She hunts you relentlessly through Waterfall, because one more human soul could free her people. Away from battle she's loud, competitive, fiercely loyal and a big fan of anime. Her friendship with Papyrus, whom she trains, is one of the funniest relationships in the game.
Alphys
Royal Scientist
Alphys is a shy, anxious lizard scientist who guides you through Hotland by phone, mostly by hacking the obstacles she claims not to have created. She loves anime, has a crush on Undyne, and carries guilt about something in her past research she isn't ready to talk about. What she's hiding is one of the game's darker discoveries.
Mettaton
Underground TV star · Robot
Mettaton is a glamorous robot built by Alphys, and the only celebrity in the Underground. He turns every encounter with you into a TV show: a quiz, a cooking segment, a musical, a dramatic news report. He's vain, ridiculous and having the time of his life. Under the boxy body there's a surprisingly personal story about wanting to be seen as you really are.
Asgore Dreemurr
King of the Underground · Boss monster
Asgore is the king, and every monster talks about him as a kind, gentle soul who loves gardening and tea. He's also the one who ordered that fallen humans be killed, so their souls could be used to break the barrier. By the time you reach him, you've heard so much about him from his subjects that the meeting feels heavy. He's not a villain; he's a grieving man who made a terrible decision.
Areas and bosses
The Underground is divided into distinct regions, each with its own mood, music and major encounter. You travel through them in a fixed order.
| Area | Mood | Main encounter | Notable monsters |
|---|---|---|---|
| The Ruins | Quiet, purple, tutorial-like | Toriel | Froggit, Whimsun, Napstablook |
| Snowdin | Cosy snowy village | Papyrus | Sans, the dog guards, Snowdrake |
| Waterfall | Glowing caves, melancholy | Undyne | Monster Kid, Shyren, Mad Dummy, Temmie |
| Hotland | Lava, labs and TV shows | Mettaton | Alphys, Muffet, Royal Guards 01 and 02 |
| The Core and New Home | Industrial, then grey and quiet | Asgore | Final encounters vary by route |
Most bosses can be spared, but each one asks something different of you. Toriel has to be outlasted with mercy, Papyrus wants to have a battle he can be proud of, Undyne needs you to survive long enough to escape, Mettaton wants ratings, and Muffet the spider wants to be paid. Each fight has its own leitmotif, and track titles like "Bonetrousle," "Spear of Justice" and "Death by Glamour" are almost as famous as the characters.
Minor monsters and side characters
Undertale's random encounters are characters too. Each monster has its own personality and its own peaceful solution, which is why players remember so many of them.
Napstablook
Shy ghost
A melancholy ghost who lies down to pretend to be asleep, cries attacks at you and makes music in a little house in Waterfall. Gloomy, sweet and easy to love.
Monster Kid
Undyne's biggest fan
An armless young monster who follows you around talking about how cool Undyne is, and keeps falling over. One of the best small characters in the game.
Muffet
Spider baker
A many-armed spider girl who runs a bake sale and has been told humans hate spiders. She's polite, ruthless and very interested in your money.
Temmie
Temmie Village
A cat-dog creature from a village of identical cat-dog creatures, who speaks in excited misspellings and wants to go to college. Named after artist Temmie Chang.
Grillby
Bartender
A quiet fire elemental who runs the bar in Snowdin where Sans is a regular. He barely speaks, which only adds to his mystique.
Gerson
Shopkeeper
An elderly turtle who runs a shop in Waterfall and knows the history of the Underground better than anyone. He's known Undyne since she was a kid.
Doggo, Lesser Dog and Greater Dog
Royal Guard dogs
Snowdin's canine sentries. Doggo can only see things that move, Lesser Dog's neck grows when petted, and Greater Dog is a big, armoured puppy who just wants attention.
Dogamy and Dogaressa
Married axe-wielding dogs
A hooded dog couple who patrol together and sniff you out. Roll in the dirt and pet them to show you're just a puppy.
Royal Guards 01 and 02
Armoured guards
Two armoured guards with an unspoken crush between them. The peaceful way through is to help one of them say it.
Mad Dummy
Possessed dummy
A ghost living in a training dummy who's furious with you for something you did in the Ruins. Physical attacks don't work on him.
Froggit and Whimsun
Ruins monsters
The first monsters you meet. Froggit can be complimented, and Whimsun is so anxious it bursts into tears and flies away.
Burgerpants
Fast-food employee
A miserable young cat working at Mettaton's burger restaurant, who dreams of fame and despises his boss.
The three routes
Undertale tracks what you do. Its stats are named LOVE and EXP, and the game eventually tells you what those letters stand for. Each route gives the same characters very different fates.
Neutral
The default outcome of a first run, where you spare some monsters and kill others, or don't finish the extra steps for the best ending. The ending is a phone call that changes depending on who lived. It's meant to make you want to try again.
True Pacifist
Spare everyone, complete a Neutral run, and befriend Papyrus, Undyne and Alphys. This unlocks the extra story, the full truth about the Underground's history and the game's real ending.
Genocide
Kill every monster in each area until no more will appear. The game changes tone completely, characters react to what you've become, and the final encounters are the hardest in the game. Undertale remembers that you did this, even after you start over.
Spoilers: the twists behind the cast
- Flowey is Asriel Dreemurr, Toriel and Asgore's son, brought back without a soul by Alphys's experiments. Unable to feel love, he spent countless resets doing everything to the Underground out of boredom. On the True Pacifist route you fight him in his restored form and save him, though he can't stay that way.
- Chara is the first human who fell, adopted by the royal family. The name you enter at the start of the game is theirs. Chara and Asriel's deaths led to Asgore's war on humanity and Toriel leaving him. On the Genocide route, Chara becomes the force guiding you.
- Alphys's secret is the True Lab, where her attempts to use human "determination" on dying monsters created the Amalgamates, melted-together creatures their families believe died long ago.
- Mettaton is a ghost, Napstablook's cousin, who left his family to live in the body Alphys built him.
- Sans made Toriel a promise through the Ruins door to protect any human who came through. He knows about resets, and on the Genocide route he's the final judge of what you've done.
- W. D. Gaster is a former Royal Scientist who is only hinted at through hidden text and fragments. Very little about him is confirmed.
What the characters are really about
Undertale is a game about mercy, and about taking responsibility for what you do in a game. Most RPGs reward you for killing. Undertale asks why you're doing it, then gives its monsters enough personality that you start to care. Papyrus believes you can be good, and that faith is hard to betray. Toriel and Asgore have both made choices out of grief. Flowey is what someone becomes when nothing feels real any more, which is uncomfortably close to how players treat game worlds.
Its cast is a good illustration of how a redemption arc can run in both directions, and of how sympathetic antagonists like Asgore fit into our villain types guide. If you're writing about the game, our spoiler etiquette guide applies twice over: Undertale is built around discovery.
Fans of Undertale's mix of cute characters and unsettling undertones often enjoy Five Nights at Freddy's and Dandy's World, which both build horror out of friendly-looking characters.
A note on Deltarune
Deltarune is Toby Fox's follow-up project, released in chapters since 2018. Many familiar faces, including Toriel, Asgore, Sans, Undyne and Alphys, live in an ordinary small town with new roles and relationships, alongside new leads Kris, Susie and Ralsei. It isn't a direct sequel, and it doesn't need Undertale's context, though it rewards players who know the original.
All Undertale character names A–Z
A–C
- Alphys — Royal Scientist
- Amalgamates — True Lab
- Asgore Dreemurr — King
- Asriel Dreemurr — Prince
- Burgerpants — Hotland
- Chara — First human
D–G
- Doggo — Royal Guard
- Dogamy and Dogaressa — Royal Guard
- Flowey — Antagonist
- Frisk — Player character
- Froggit — Ruins
- Gaster — Hidden
- Gerson — Waterfall
- Greater Dog — Royal Guard
- Grillby — Snowdin
L–N
- Lesser Dog — Royal Guard
- Mad Dummy — Waterfall
- Mettaton — Hotland
- Monster Kid — Waterfall
- Muffet — Hotland
- Napstablook — Ruins / Waterfall
P–S
- Papyrus — Snowdin
- Royal Guards 01 and 02 — Hotland
- Sans — Snowdin
- Shyren — Waterfall
- Snowdrake — Snowdin
T–W
- Temmie — Waterfall
- Toriel — Ruins
- Undyne — Royal Guard
- Whimsun — Ruins
Frequently asked questions
Who is the main character of Undertale?
You play as a human child who falls into the Underground, the world where monsters were sealed away. The game lets you name a character at the start, but the child you control is revealed late in the best ending to be called Frisk. The name you choose at the beginning actually belongs to someone else.
Are Sans and Papyrus brothers?
Yes. Sans is the short, lazy older-seeming one who tells puns, and Papyrus is the tall, loud, enthusiastic one who wants to join the Royal Guard. Both are named after fonts, which their dialogue boxes use.
Who is the hardest boss in Undertale?
Most players say Sans, who you only fight on the Genocide route. His battle breaks several of the game's normal rules and is designed to be punishing. On other routes, Undyne and the final battles tend to be the toughest.
Who is Flowey?
Flowey is the friendly-seeming flower who greets you at the start of the game and immediately tries to kill you. He's the game's recurring antagonist. His true identity is a major spoiler; it's covered in the marked routes section on this page.
How many endings does Undertale have?
There are three main routes: Neutral, True Pacifist and Genocide. The Neutral route has many variations depending on who you spared or killed, so the total number of distinct endings is large. True Pacifist is generally considered the main, intended ending.
Is Deltarune a sequel to Undertale?
Not exactly. Deltarune is a separate game by Toby Fox that uses many of the same characters, such as Toriel, Sans, Undyne and Alphys, in a different world with different relationships. You don't need to play Undertale first, though you'll recognise a lot of faces if you have.