Don’t Kill Anyone in Undertale – True Pacifist Ending Guide

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Undertale is one of the most unique and entertaining games in recent memory. This game takes classic RPG elements and combines them with rich characters, a unique combat system, great music, and multiple paths and endings for a truly fulfilling and amazing RPG experience. Undertale was even voted “Greatest Game of All-Time” by GameFAQs voters! While that title may be a bit over the top, Undertale delivers a one-of-a-kind game that any RPG fan should experience.

Undertale‘s greatest feat is to turn your view of what an RPG and its characters upside-down. It features a human stuck in the underground land of monsters and the journey to return home. Although a short game, the world presented is so rich it demands multiple playthroughs. There are numerous endings available in Undertale, but the most satisfying is the Pacifist or True Ending.

This guide will detail the steps necessary to achieve a the True Ending of the game. It will not be a step-by-step walkthrough and will not detail how to complete puzzles or defeat every enemy, however the final section will be a Bestiary with instruction on how to defeat each enemy of the game.

WARNING – Spoilers Ahead!: This guide will assume you have completed the game already, and while spoilers will be kept to a minimum, it would be impossible to present a guide without them. If you have met all the requirements of pacifism on your first play-through, you are able to reload your save after the final boss and backtrack to unlock the True Ending.

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The Basics: How to Achieve the True Ending

The number one rule to achieve the True Ending is do not kill anything! This is the most important and obvious component of the Pacifist run. Every enemy you encounter can be defeated without violence; killing even one monster will shift you to the neutral path. This necessary play-style will yield no experience, leaving you at Level 1 with 20 HP for the duration of the game. This is a handicap, but one that can be overcome with planning, plenty of healing items, and conservative play. Using some tricks this guide provides is imperative to late-game success.

Pacifist Checklist

  • Kill no enemies; gain no LVL or EXP. (Dummy in Ruins and Mad Dummy do not count toward this goal.)
  • Befriend and visit Papyrus at his house after the boss fight against him.
  • Give Undyne water after the boss fight against her.
  • Visit Undyne at her house and complete the side mission inside.
  • Get through the Core and Spare Mettaton EX.
  • If this is your first playthrough, defeat King Asgore and Flowey. You may return to the save point before King Asgore and complete True Ending without playing the entire game over again.
  • Receive phone call from Undyne at MTT Resort. Refer to True Lab section to complete the True Ending.

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Introduction / The Ruins

The beginning of the game is basically a tutorial, and not very difficult to traverse. After your introduction to the friendly flower, Flowey, you are handed off to Toriel to teach you the basics of the game.

Tips for The Ruins

  • If you stay in the area Toriel tells you to, you will receive cell phone calls with some unique dialogue.
  • Make sure to buy a Spider Donut! You may have to grind for some extra gold, but this item is invaluable for a later encounter.
  • If this is your first play-through and you must face King Asgore, hold on to the Butterscotch Pie. The pie is not necessary if you are replaying the game for the True Ending.

Most of the regular enemies here are pretty easy to Spare; if you get stuck on a tough enemy, reference the Bestiary in this guide. One of the more troublesome enemies in this are is Vegetoid. There are two ways to peacefully resolve combat with this enemy. The first is to damage him until he becomes “bruised” and Devour him for 5 HP. Just be careful not to kill him! Three medium attacks should be about right. The second, and more conservative option is to select Dinner. You must run into one of the green sections when he attacks to unlock the Spare option.

Pacifist Boss Tips: Napstablook

  • Spare Napstablook, the sad ghost in the Ruins, by using Cheer a few times.

Make your way through the easy puzzles and explore side areas for extra items; soon you will arrive at Toriel’s home. There isn’t much to explore here, but first-time players should check everything possible for some background and insight. Sleep in the bed provided and you will awaken to the Butterscotch Pie and be able to advance.

Talk to Toriel and follow her into the basement. She will try to protect you by preventing you from leaving; this is the first boss battle of the game.

Pacifist Boss Tips: Toriel

  • Use Spare on every turn to proceed. It takes a lot of Spare attempts to finally end the battle!
  • Toriel will damage you, but if your HP gets low her attacks will avoid you.

Once completed you will be granted access to the next section of the game, Snowdin.

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You gotta love sans and Papyrus, right? These skeleton brothers will be your guides for the next chapter of the game. The forest and town of Snowdin are also fairly easy, but one of the most entertaining sections of the game. Enjoy yourself and follow the brothers through the area.

Tips for Snowdin:

  • The snowman piece you receive early in the area is not an essential item; it simply opens some dialogue if you are carrying it upon completion of a Neutral playthrough.
  • You are able to stay the hotel for free, even though the innkeeper says it will cost 80g, and it will raise your max HP by 10.
  • If you search all the snow poofs you will find 30g!
  • The Bisicle consumable is one of the most useful for the Pacifist play-through. It heals 11 HP and can be used twice, making it like two healing items in one! It also has a great healing number, as you will only have 20 HP throughout the game. The Bandana is also worth buying at this shop.

Pacifist Boss Tips: Lesser Dog, Greater Dog, Doggo, Dogi

  • There are multiple dog-themed enemies and bosses here. Throwing your initial weapon, the stick, will allow a Spare with just one use. There are other ways to peacefully resolve these battles, but the stick is the easiest and awards gold each time.

After a series of dastardly puzzles you will find yourself in the town of Snowdin itself. If this is your first visit to the area, take your time and explore. There are a lot of items and characters to interact with. Once you are done looking around, head east for the showdown with Papryus.

Pacifist Boss Tips: Papyrus

  • This boss fight is one of the most entertaining in the game. Papyrus’ “special attack” turns your soul blue and leaves you on the the floor of the fighting area. Papyrus will use bone attacks; jumps that are the right height and well-timed are needed to get past this boss.
  • Use the “Flirt” option during the battle and survive to unlock a date with Papyrus later.. Survive Papyrus’ Special Attack, and he decides to… ahem… Spare you. Now you can go on to the next area, but there is some unfinished business before you go.

Head back to town and find Papyrus outside of his house. Talk to him to start your date/hang-out. Answer however you’d like; there is no consequence to the choices you make in this section. Finally, make sure to grab a bite to eat with sans before you finally head to the next section, Waterfall.

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Waterfall: Part 1

Waterfall is where things start to get real. There is nobody to guide you here, just the Royal Guard leader Undyne chasing you the entire time. She is a pretty terrifying adversary! If this is your first time through, read the stories on the walls and listen to the talking flowers for some back-story. There are some simple puzzles and paths to traverse here, but nothing too tough.

Tips for Waterfall: Part 1:

  • Make sure to set up the flowers in the initial puzzle to the southeast for a special consumable.
  • There is a good defense item, the Dusty Tutu, behind the first waterfall with falling rocks.
  • During the Undyne spear chase, weave diagonally to avoid spears more easily.
  • During the Undyne floor spears, the faster the better, but halt completely if you see a spear pop up in front of you. Use the path below as a guide for where to go.
  • Do not buy Nice Cream from the vendor. It is actually more expensive than in the previous area and there will be a better vendor shortly.

Pacifist Boss Tips: Mad Dummy

  • At the end of this section you will run into the Mad Dummy. He will use other dummies to attack you; simply make sure they are aiming toward him to inflict damage. There is not a Spare option for this boss, just use his minions to damage him enough to end the fight.

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Waterfall: Part 2

Tips for Waterfall: Part 2:

  • To the southeast of the lantern path is Temmie Village. This is a very helpful area, as it houses the only vendor in the game that you can sell items to. Unload your old weapons and armor for some decent gold.
  • You can spend 1000g to send Temmie to college and unlock some very powerful Temmie armor. This armor is very expensive, but becomes cheaper according to how may deaths you rack up. The process is time consuming and expensive and takes a ton of commitment to gold farming. It is not recommended.
  • The Turtle Vendor has some of the best items for the Pacifist run. The Torn Notebook doesn’t deal much damage, but increases invincibility when hit. This is the best weapon for the Pacifist play-through, as you will never attack. The Cloudy Glasses also increase invisibility, but a higher defense item is generally a better choice.

Make your way though the second section of Waterfall, making sure to visit Temmie Village, the Turtle Vendor, Ghost House, and the snail races. Snail races aren’t worth the time, but they are fun to see. The Undyne boss fight is the next hurdle to overcome, and it is a tough one! Make sure you have plenty of healing items and your reflexes at their sharpest!

Pacifist Boss Tips: Undyne

  • This is another very unique fight. Instead of using your soul to avoid attacks you will control a shield to protect it. The key is to get the timing of Undyne’s attacks and flee as soon as it becomes an option.

With quick reflexes and no deaths, you should arrive in Hotworld in 3 or 4 Flee attempts. The yellow arrows Undyne shoots at you will swing around and attack from behind, so be prepared. This is a difficult battle and may take a few tries to overcome. Make sure you give Undyne some water when you arrive in Hotworld to befriend her and backtrack to her house for a get-together.

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Hotworld: Part 1 – Lab

Hotworld is the final area of the game. If you have kept to the rules of the Pacifist play-through, and are on the Neutral playthough, King Asgore will be at final section, followed by a chance to rewind and receive the True Pacifist ending.

The Royal Scientist, Alphys, will be your guide for the final stretch. She will attempt to help you through puzzles and bosses of the area; just be prepared for your cell phone to ring…constantly. Mettaton, a TV star robot of Alphys’ creation will be your nemesis. Make sure you have plenty of consumables on hand, as there are plenty of tough enemies in Hotworld.

Hotworld: Part 1 Tips:

  • After some quiz show fun with Mettaton and some puzzle traversing, you will find the first boss of the area, the Royal Guards.
  • After some more puzzles and an encounter with Mettaton, you will find yourself at the next boss, Muffet.

Pacifist Boss Tips: Mettaton [First Encounter]

  • Watch Dr. Alphys’ hands for clues! Cheat to earn victory in this battle.

Pacifist Boss Tips: Royal Guards

  • The Guards attacks can be pretty powerful, but defeating them is easy. “Clean” 02’s armor until he removes it and “whisper” to 01.

Pacifist Boss Tips: Muffet

  • Muffet is one of the most difficult bosses yet. but if you bought and saved that Spider Donut from the Ruins you can get a peaceful resolution in one turn. Once in battle, simply eat the donut and you are able to Spare Muffet. Nice!

Keep going and after another fun-filled Mettaton encounter, you will find the MTT resort. This is pretty much the last haven of the Undertale world, so stock up accordingly!

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Hotworld: Part 2 – MTT Resort & Core

The first step here is to go have a bite to eat with sans. After a nice chat over a meal you are free to explore the area on your own.

Hotworld: Part 2 Tips:

  • The vendor to the right of the building sells some unique items, but nothing vital. The mysterious key opens the Ghost House in Waterfall.
  • The vendor inside the building is extremely helpful to help you survive the next boss fight. Stock up on Glamburgers and other consumables here!
  • You can sleep in the hotel for 200g to receive the 10 max HP bonus, but it isn’t really worth the gold when you can fast travel back to Snowdin with the ferryman for a free 10 HP boost..

The next stop after the MTT building is the Core. There are a few ways to get through this area, but the easiest is to head west and complete the puzzle to open the east walkway. The far north contains a few enemies to open the same walkway and is not recommended. There is a trashcan to the northeast that contains 100g and another to the far northwest that contains a Glamburger. Search the area until you run into them.

To the far northeast is the path to the end of the line. It contains a save point, a door, and an elevator. Once you are ready, and loaded with healing items, head through the door for the final showdown with Mettaton.

This Mettaton boss fight is pretty crazy. You need to get the audience over 10,000 to succeed. There are a few strategies to accomplish this. Pose will grant some audience points; the lower your health the bigger the number. Boast will grant faster audience gain, but if you get hit on the next turn you will lose audience. Eating Glamburgers or other MTT food will grant +500 audience. The best strategy is to Pose, Defend, and heal with MTT food when your health gets low.

Pacifist Boss Tips: Mettaton EX

  • When Mettaton gives you the opportunity to shoot his heart, use your projectiles to deal damage while avoiding his attacks.
  • During the “disco ball” attack, use your projectiles to change the color of the lasers. When a blue laser is approaching, sit still. When a white laser is on the way, shoot the disco ball to change it to blue.
  • Mettaton will ask you to write and essay at some point. Type “legs” or “toby” to get a little audience bonus.

Once you reach 9,000 – 9,500 audience, eat some MTT food to get you to that magic 10,000 number and complete the battle. On a Neutral run, the next step would be to head into the final battle with King Asgore. On the Pacifist run, however, you will head back to MTT Resort and receive a phone call.

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Neutral Ending

After defeating Mettaton EX you will move on the New Home. This is a different version of Tariel’s home and has a few useful items. Head to the bedroom and pick up and equip the Heart-Shaped Locket and Worn Dagger. These items will help out a lot in the battle against King Asgore. There are two keys in the upper levels of the house. Search the rooms for the keys and make sure to search the items for some extra story. Unlock the chain to the basement and head on down. A familiar character will stop by on the way for a brief conversation and some information on the true nature of the game that will blow your mind.

Pacifist Boss Tips: King Asgore

There is no way to peacefully end this fight. You must fight King Asgore. Make sure you are loaded with healing items and have your strongest weapon and armor equipped. This battle will be very, very difficult if you have stuck to the Pacifist checklist.

  • Make sure you have your Butterscotch Pie in your inventory for this battle. Using it will reduce Asgore’s ATK and DEF for the duration of the battle. You can also Talk to him 3 times to lower his ATK and DEF.
  • King Asgore’s attacks are much like Tariel’s, but he offers no mercy. He will sometimes use a colored attack that is prefaced by his eyes. If you see orange you must move during the attack, if they are blue you must sit still.
  • Try to avoid his attacks as much as possible and attack him every turn; eventually he will kneel and the fight will be over.

You now will have the option to Spare or Kill King Asgore. You must Spare him to unlock the True Ending! You will be visited by an old friend and things will start to get…weird.

Pacifist Boss Tips: Flowey

Once Flowey shows up, things start to get completely insane. The game will crash and reopen in Flowey’s nightmare world. He will mutate into a god-like killing machine, triggering the final battle of the Neutral play-through.

  • The Flowey boss battle is long, difficult, and annoying. His attacks are unavoidable and constant, but don’t do much damage. Dodge as best you can, but expect to get hit often. Attack at every opportunity given to advance to the next phase of the battle.
  • Flowey will now summon his souls to attack you, but you are able to use them to your advantage. You must find the Act button and activate it to turn the white, damaging attacks into green, healing attacks.
  • There are 6 souls to get through; once completed they will combine their powers to reduce Flowey’s DEF to 0 and allow you to finish off this abomination. Avoid his attacks as best you can and attack at every opportunity to end the battle.

You can Kill or Spare Flowey; is doesn’t effect you ability to achieve the True Ending.

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True Lab & True Ending

Once you receive the phone call and do a bit of running around for Alphys and Undyne, you will be able to access the True Lab. This area requires you to find 4 colored keys and their corresponding locks, as well as defeat some extremely tough enemies. These enemies are so challenging this section of the guide will detail how to dispatch them.

Note: Make sure to check out the wall notes and VHS tapes in True Lab for some great information about the characters of the game and the monster world.

Pacifist Boss Tips: Memoryhead

The first key to find is the Red Key, and is located to the west. Check the sinks until the Memoryhead trio appears. These guys are pretty tricky to defeat; you must use Cell and then Refuse to unlock the Spare option. They will drop the Red Key after the battle; the lock is in the same area.

Head east into a room of beds. You are able to sleep in the first one if you wish. The Yellow Key is in the bed that looks different from the rest. Head north for the next key.

Pacifist Boss Tips: Endogeny

Once in the next section, head east to a hallway with a block of fans and hit the switch. A crazy dog-monster named Endogeny will appear, and it takes some work to win this fight. Beckon, Pet, Play, Pet, and Pet are the actions needed to open the Spare option. Be weary of the homing attacks! After this monster is defeated, head west and find the shower stall with the Green Key inside.

Pacifist Boss Tips: Lemon Bread

Keep heading west and activate the save point. Surprise! It’s actually the monster Lemon Bread! Use Unhug, Hum and Flex to Spare this one. The lock for the Yellow Key is just ahead, as well the VHS tapes mentioned earlier.

Pacifist Boss Tips: Amalgamate

Heading even farther west, search the fridges for the monster Amalgamate; Joke three times to open the Spare option. He will drop the Green Key; the lock for the Blue Key is also in this area.

Head back to the room of beds and take the east hallway. You will run into Reaper Bird; use Pray, Mystify, and Pick On to end this battle. The lock for the Blue key is here. Now all the locks are open and it is time for the final showdown! Prepare yourself for madness!

Pacifist Boss Tips: Asriel

Asriel Dreemurr is the final boss to defeat in the Pacifist play-through. Asriel is an extremely difficult boss, but the good news is you cannot really fail in this fight!

  • There isn’t much to do here except avoid Asriel’s attacks. The Hope option will reduce damage for the next turn and the Dream option will fill all empty inventory slots with healing consumables. His attacks are intense, but he will tell you what’s next so you are able to prepare. Hang in there and do your best to dodge; eventually you will be able to move onto the next part of this insane battle!
  • After a while the fight will switch gears and Asriel will stop attacking; now you must free the souls of all your friends. The battles will mirror the ones earlier in the game, just use actions for each fight and eventually you will free everyone.
  • The last soul to free is Asriel’s; once you completed this task the adventure is over and you have successfully completed the Pacifist run and can experience the True Ending!

Before you head home and truly end the game, you can backtrack through the world and talk to all the NPC’s. New dialogue will be unlocked and if you make it all the way back to the beginning of the Ruins you can talk to a special character.

Once you end the game, credits will roll. If you are able to avoid all the names in the credits, which is nearly impossible, you will unlock the Mystery Door in Waterfall!

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This section will list all the monsters in Undertale and provide the actions needed to Spare them for the True Pacifist ending route..


  • Froggit – Compliment
  • Whimsum – Console
  • Moldsmal – Flirt
  • Migosp – Get him alone, Talk
  • Loox – Don’t Pick On
  • Vegetoid – Dinner; lower health and Dine


  • Snowdrake – Laugh at his jokes
  • Ice Cap – Ignore, Ignore, Steal Cap, Compliment
  • Jerry – Ditch Him!
  • Lesser Dog – Pet x8; Use Stick
  • Gyftrot – Undecorate x4
  • Dogi – Roll in Dirt, Resmell, Pet each; Use Stick
  • Greater Dog – Beckon, Pet, Play, Pet, Pet; Use Stick


  • Aaron – Flex x3
  • Woshua – Clean
  • Shyren – Hum, Hum, Conduct, Hum
  • Temmie – Temmie Flakes, Talk
  • Moldbygg – Unhug

Hotland/ The Core

  • Vulkin – Encourage, Hug
  • Tsunderplane – Approach, only hit green area on attack
  • Pyrope – Heat Up
  • Madjick – Stare at Orbs
  • Knight Knight – Hum x3
  • Whimsalot – Pray
  • Final Froggit – Mystify
  • Astigmatism – Do what he tells you

True Lab

  • Memoryhead – Cell, Refuse
  • Endogeny – Beckon, Pet, Play, Pet, Pet (or stick)
  • Amalgamate – Joke x3
  • Lemon Bread – Flex, Hum, Unhug
  • Reaper Bird – Pray, Mystify, Unhug

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