undyne undertale guide

Undyne Undertale Guide – StrongFish91

Undyne is one of the premier NPC characters in Undertale. She is faced as an enemy when first encountered. This character’s arc will ultimately play out in quite a few ways. That depends entirely on you, the player.

In this popular Indie Game title, the player’s choices do change the story, and the way characters will react to you. Undertale takes the RPG genre of video games more literally and gives a more dynamic life to side characters such as Undyne.

A fish-like humanoid, Undyne is the leader of the Royal Guard. She is known as StrongFish91 on the UnderNet and is a lover of Anime and a hater of soda.

When you first meet her she will chase you through the entirety of the Waterfall section as your enemy. Her fate afterward depends on how you deal with her.

In this Undyne Undertale guide, we’ll explore your interactions and how best to handle the battles guaranteed to come your way with this eye-patch-wearing warrior.

Some Key Info Beforehand

  • First Encounter: Waterfall.
    Pacifist Difficulty: Medium.
    Genocide Difficulty: Hard.
    Personality: Strong, stubborn, caring, and very dedicated.
    Battle Box Type: Deflect and Dodge.
    Additional Content: A cooking side quest and a letter side quest.

What is Undyne?

A fish-human hybrid in design. More importantly, an honor-bound warrior woman who is head of the royal guard. To her and her people, you are the danger, and Undyne will not let you harm anyone.

She wields a spear, is revered by many, and looked up to by some of the earlier characters, which you will learn more of if you let them live, of course.

How does Undyne Fight?

Undyne will use a plethora of different spear-like attacks in the battle box. Aside from dodging these attacks, you will also have to pay attention to the color of your SOUL.

During the battle, your SOUL’s color will be changed. Your SOUL will start GREEN and then be switched to RED. Remember this as it is important to note depending on what you plan to do.

Unlike some BOSS fights that are harder when trying to achieve a PACIFIST route, Undyne is more challenging when trying to kill her. Honestly, good for her.

Green Soul

You cannot flee or make ground talking when in GREEN soul mode against Undyne. Therefore, you must do your best to deflect whether you choose to attack or attempt mercy. Don’t worry; Undyne instructs you on how to do this to make it a ‘fair’ fight.

Spears will come at you from all sides, some slow, some fast, and some switching the directory they assault. You must choose which direction to guard in the Battle Box to stop them from dealing damage. Although the difficulty spike as the spears speed up can be pretty high, they will only do five damage if they strike, and there won’t be too many.

Choose anything besides ATTACK if you are trying for a Pacifist run until you are changed into RED soul mode.

Red Soul

Under Red Soul, you can flee. Fleeing is the only real option to manage the PACIFIST or NEUTRAL route in the game. If you do choose to fight, however, or for some reason can’t flee outright, the attacks are as follows.

The Battle Box, or the square where you take battle actions, becomes smaller. Spear launch up at you from below, doing five damage per hit. You can find a safe spot between the left and center spears to deal with this assault easier.

The Battle Box returned to normal; she will launch a volley of continuous spears you must dodge that each does five damage per hit.

When she changes the soul mode to RED from GREEN at the end of an attack, she’ll throw a single spear that does four damage. However, it won’t be done if you are fighting her when she attacks as “Undyne the Undying.”

Suppose you are on the route of a pure Genocide run(killing everything). Undyne will have two more attacks in RED soul mode.

She will throw rings of spears that enclose on you while they rotate and a similar attack in which they don’t. In the second version, they head straight towards the SOUL. They will travel in the direction they started at for some seconds before fading.

How Long Does it Take for Mercy?

It’s a long one. Here are the essentials to know for making it as quick as a process as possible.

  • Make sure to save the Monster Kid before the fight.
  • Deflect all the GREEN mode attacks; it should be about three rounds until she goes into RED mode.
  • Flee.
  • You’ll have to repeat that probably three times with increasing difficulty.
  • Always run towards the Hotlands.
  • Undyne gets distracted by a sleeping Sans eventually.
  • Run across the bridge further into the Hotlands.
  • Undyne catches up but is dying of thirst.
  • Give her some water.
  • You’ve done it.

What if I want to Kill Undyne?

You can accomplish this in the very first encounter. The GREEN mode attacks will slowly increase in speed as her HP goes down. When she finally reaches 0 life, she will not simply die. She will fight to stay alive to save everyone and protect them.

No matter how intense this dialogue may seem, you’ve reached the point of no return. Undyne is going to die now.

She will first continuously come back to life. However, her attacks will be slower and slower as her eventual demise comes around.

Soon, her body will deteriorate, no longer able to hold onto her strong spirit. That is when the fight will end, and it is the only way you can “kill” her.

Travel Map

You do get attacked TWICE on the TRAVEL MAP by Undyne. The attacks are in the form of mini-games that can kill you. So, pay attention to how easy they can be as long as you don’t panic.

First, she will appear above you and summon three spears to shoot at you. If they connect, you’ll enter a quick combat-like Battle Box and get assaulted by spears each time.

To dodge these spears, you can stay near the bottom of the path. Then,d run diagonally toward the top once they are launched. This tactic can be a bit more tricky when the path goes up and down. Don’t worry; you won’t lose much life if you get hit once or twice.

Second, she will launch spears from beneath you as you traverse some strange wooden path over what is essentially darkness. If they connect, the same Battle Box and damage will occur that occurred before.

Quickly move to a spot with no blue light to avoid being hit. Being patient and picking your movements here makes it pretty easy to avoid. However, the path is odd. You will need to head forward and down, then forward again to exit. At the end of the trail, she will drop you into a trash heap with more water.

The Undying Waterfall

When you enter Waterfall, subtle hints on the eventual meeting with Undyne become more than hints when the armor-clad warrior lurks above you. You also first meet the Monster kid here.

He is a huge Undyne fan and assumes you must be too because everyone is. He’s never seen a human, so he doesn’t think twice about how different you look and treats you as he would any other kid.

Shortly after, Papyrus will give you a call. You’ll note he met with Undyne earlier and admitted to not catching you but had a hard time saying it out if you let him live. If you didn’t let him live, this scene doesn’t happen.

When(if) Papyrus calls you, he’ll ask if you’re wearing exactly what you are wearing. (Being honest or lying doesn’t seem to impact the story significantly). When he calls you again after Undyne has attacked you on the TRAVEL MAP, Papyrus says he’s glad you told him the opposite of what he should tell Undyne so they wouldn’t find you, which you didn’t. Aha.

Undyne will almost catch you once, but grab up the Monster Kid instead and drag him off. That always kind of cracks me up. I like this kid, what can I say.

You can pick up an Umbrella shortly after to do two things, unlock a particular cavern by giving it to a statue. Watch the statue again after giving it an Umbrella to wait for the secret code needed on a piano in a path just behind you.

Then take another Umbrella to initiate the following.

The Monster Kid will follow you, and you’ll hear him go on about Undyne a bit. It’s unique, and story building, but also you need him to follow you so you can climb on his head to move forward.

Eventually, the kid will get in front of you again when she has you cornered, and she’ll drag him off home giving you time to move out. Only, he comes back.

As you’re crossing a bridge, he’ll tell you how he knows you’re human and ask you to say something to make him hate you.

I admit to always saying no and saving him when he runs off instead of letting him fall. If you’re playing for a Genocide finish, you shouldn’t save him, though. Undyne will start with less health and hate you more should you just let him fall, especially if you’ve killed Papyrus.

After the bridge incident, you will finally face Undyne in battle. Save the game beforehand. It truly isn’t that easy your first run-through. To do that, when she asks you to step forward, quickly step back instead, and a save star will have appeared.

Her dialogue will be different depending on what you’ve done. If you’ve killed Papyrus, it will be focused on that. If you’ve killed all the dogs, she’ll be in light mourning of her friends’ deaths. If you’ve killed nothing, she’ll mock you. Mostly to try and convince herself you’re pretending to be good.

Prove her wrong. You can do it.

Genocide Mode for Undyne Ends Here

If you are playing Genocide or just want to kill her here, fight and achieve victory as described earlier in this Guide. If not, the story will go on.

Pacifist or Neutral Mode Continues the Tale

As soon as you have the chance to flee from battle, take it. Hold the direction button to run toward Hotlands as soon as you see the word, Escaped!

You will probably end up fighting Undyne three more times. Eventually, you will pass a sleeping Sans, and she will be so annoyed by this she’ll get distracted as you continue over a bridge into the Hotlands.

She’ll come crawling up and asking for water. You’ll see a water cooler nearby, giver her a drink if you want to save her. If you do so confused, she will return to Waterfall.

If you don’t, she doesn’t die but develops Heatstroke and won’t be your friend. That’s about the end with her there.

Befriending Undyne

Once all is said and done, if you did give Undyne Water, you might as well get all the perks of this choice. That is, she will only befriend you; if you have 0 EXP, as in, you haven’t killed anything.

With these conditions met, you can go back into Waterfall and find Undyne’s house. I would suggest doing so after meeting Alphys and not killing Mettaton.

It’s the cool, two-faced style house next to the Ghosts home. There, you can meet Undyne. Papyrus will cool her off and present befriending you as a challenge.

You’ll learn a lot more about this Royal Guards life. You’ll do some cooking with her, get into a mock fight, and grow closer. You may even learn about her affection for Alphys.

I should note that her house kind of gets engulfed in flames. So she moves to Papyrus and Sans house aftwerward. Make sure you searched every room before completing the “date” with Undyne.

Optional Quests

With Undyne befriended and the above finished, later on in the game, you should be able to return from the CORE to the MTT Resort. There you’ll get a call from Undyne asking for your help. The help is to give Aplhys a love letter. Which Alphys will mistakenly think is from you.

A few awkward scenes later and Undyne and Alphys confess their feelings for one another. Which somehow ends with Undyne tossing Alphys into a trashcan.

The end of this comically comes about when Undyne tells Alphys to work on their self-image, and Alphys agrees before leaving, hinting at their future. Before you go, though, Undyne stops you to ask you if Anime is real.

Undyne is the most badass fighter in all of Undertale, by the way. Who thinks Anime is what real human life is like above ground. The balance of a character like Undyne being both comical and emotionally realistic is brilliantly handled in this short RPG. Indeed, everyone is an individual.

True Pacifists Get All the Content

If you’ve followed the True Pacifist Route, Undyne will come to your aid in the battle with Asgore.

When fighting Asgore, she will appear to demand that he befriend you. Alphys and Undyne almost kiss before Flowee interrupts them and ensnares and attacks all your friends, but Undyne defends them.

As Flowee ingests the six souls, you aren’t sure what happens to Undyne and your friends at all.

In the Epilogue

If you’ve met all the conditions and come into the Epilogue to speak to Undyne, she’ll say she is happy she lost to you. She can’t wait to relax and watch Anime with Alphys now. Who she finally kisses, if only on the cheek.

Alphys faints, and Undyne laughs so hard she punches the sidewalk out of uncontrollable humor, cracking it. How the hell did you ever beat Undyne again?

Alright, strap in for A LOT of…

Plausible Endings

If Undyne is alive, and you have not done a True Pacifist Route, one of these possible endings will occur.

  • Suppose you didn’t date Alphys, and only Asgore died. In that case, Undyne will work harder to help Alpyhs be less reclusive. She’ll remind you that she and the other monsters sacrificed a great deal to help you return to the human world. Undyne tells you to appreciate life on the surface to the fullest and make that sacrifice worthwhile.
  • If you did date Alphys and only Asgore is dead, Undyne calls you with Alphys on the line. Alphys first reassures the protagonist that Mettaton is doing okay and then mentions that she is searching for a new way to free the inhabitants of the Underground.
  • If you did not befriend Undyne, spared Mettaton and Papyrus, and have killed some monsters. Papyrus lets you know Undyne plans to cross to the surface and beat you up.
  • Suppose you spared Undyne and Papyrus but killed Mettaton. Undyne doesn’t want revenge. She’s just devastated. Papyrus, not knowing what happened with Alphys (who it is implied may have taken her own life) or Asgore, who either you or Flowee will kill with this route, asks you to bring them back. It’s just a somber ending.
  • If you did befriend Undyne but then killed any monsters afterward (not including Asgore). She hates humans even more and wants to crush you for tricking her into thinking you were good. Papyrus warns you to probably never return.
  • Suppose you spared Toriel but killed a bunch of monsters and Papyrus, leaving Undyne alive. Undyne will lead a revolution banishing Toriel and becoming the Empress of the Underground, vowing to destroy humanity.

Personal Life

Undyne is one of the few female characters with a love interest that is also female in many RPG games.

She is quite a role model to many of the monsters in the Underground. Even being a piano teacher to Shyren. Though she also seems to have the most vulgar speech among the characters. The game is generally PG in dialogue, but if there is some crass language, it probably comes from Undyne.

I think she may not be that great of a cook; I base this solely on the fact the house burns down from cooking in the game.

Her relationship with Papyrus is kind of heartwarming. He doesn’t have a killing ‘bone’ in his body. (That pun may land better when you play the game).

Still, he wants to be a Royal Guard, and even knowing he probably never will be and talking down to him about his hopes for it, Undyne trains him just the same. She admires dedication, which may be what led to her falling in love with Alphys.

Any Tips?

  • I did litter most tips throughout the article this time, but I will suggest trying a True Pacifist Run if you haven’t. You’ll get the most out of the story, and it’s quite challenging.
  • I like the glove for fighting Undyne more than the Ballet shoes. As, you can tap Z up to four times almost every time with it, increasing your odds of max damage.
  • Make sure to pick up the Astronaut Food in the cooler when you fall into the garbage area during Waterfall.
  • Tying in the race with the yellow snail gives you 30g instead of 9g for winning.
  • If you want to kill her, let the Monster Kid fall.
  • If you do befriend her, make sure to go back and get all the extra content because of it.


Question: How did Undyne Lose her eye?

Answer: She had a spear accident training is a common belief. Given what she says about Asgore or how she has helped him gather six SOULS beforehand, it’s either this or from one of the other humans.

Question: Who did Undyne use to train with?

Answer: Asgore.

Question: Who is Undyne in love with?

Answer: Alphys.

Question: When can I get back to get the letter from Undyne?

Answer: You have to be playing the True Pacifist Route up until the very end. Then, when you defeat Flowee without killing it, it sends you back to the start screen. Reload your save, but be aware the internal game has saved the fact you fought Flowee and are reloading. I don’t know how it does that, but anyway, don’t fight Asgore this time.

Go through the throne room, through New Home, and the CORE back to the MTT resort. You’ll get a phone call from Undyne to meet her in Snowdin and go and do that. There’s the letter.

Question: What happens if you don’t befriend Undyne?

Answer: Many different things depending on whether or not you went True Pacifist. I cover most of this in Possible Endings above. However, if you did the True Pacifist Route and just never went back to meet her, you can still go back after you spare Flowee as additional End Game Content to do so.

You have to befriend Undyne and Papyrus as well as do the date with Alphys to unlock True Pacifist Mode.

Final Thoughts

Undyne is one of the many complex characters to come out of Undertale. She can almost come off hypocritical at first, hunting you down and calling humans murderers when having helped Asgore capture six souls. Yet, upon killing her or befriending her, you learn all her choices come from an intense passion for protecting, which she will do even for you.

There is no monster with more determination than Undyne in Undertale. Upon befriending her, you see all the many facets of this warrior. There is a good reason she has become one of the more famous faces of the game. She is a complicated emotional character and has a pretty cool design.

Also, she loves Anime. I can’t hate her.

Latest posts by Bryan Hughes (see all)

Leave a Comment

Your email address will not be published. Required fields are marked *

Scroll to Top