Undyne

Undyne is a monster that the player meets and fights in Waterfall, where she resides. She is the captain of the Royal Guard and leads them into tracking down the player for their soul. She is the third boss in the game.

Appearance
She initially appears as an imposing titan in a suit of menacing black and white armor. She later is revealed to be a fish-like humanoid creature with blue scales and a long bright red ponytail. She is incredibly powerful, as shown by her ability to suplex boulders and break rocks just by punching them.

Personality
Undyne has an intensely passionate personality. She is strong-willed and confident as a result of her training under King Asgore, and she is unmerciful to her enemies. She over-zealously believes in Asgore Dreemurr and his plan to capture seven human souls in order to break the barrier and escape the Underground.

She loves to teach, having mentored both Shyren and Papyrus in various skills, as well as instructing the player in how Green Mode works. She has a competitive spirit, but is ultimately close with those that she considers friends. She has deep-seated respect for Asgore, and romantic feelings for Alphys who has warped her perception of human history and culture due to her only exposure through the Eight Humans and anime.

She is the only monster known to possess Determination naturally aside from boss monsters, though in much smaller amounts that allow for their souls to persist after death.

Main Story
Undyne is first met after leaving Snowdin before Waterfall. Clad in her full armor, she pursues the protagonist through the entirety of Waterfall, frequently evaded or thwarted by the Monster Kid.

Neutral Route
Eventually, after Monster Kid decides to return home, Undyne confronts the character head-on in battle, where she is either killed or fled from until she becomes exhausted in Hotland. The player at this point has the choice to bring her some water from a nearby water cooler.

If the player gives Undyne the water and did not previously kill anyone, the potential to befriend her exists. During Undyne's chase sequence, Papyrus will call the player and suggest they and Undyne should hang out at her house. After Undyne's fight, the player can meet Papyrus at Undyne's house, where Papyrus immediately jumps out the window to leave Undyne and the player alone.

Undyne is initially reluctant to be nice to the player and is hostile, but she is either encouraged by Papyrus's brief return when he says she's "not up to the challenge" or realizes being the player's friend would be her "ultimate revenge". She is then determined to become "besties" by way of talking over tea, a fiery cooking lesson that accidentally burns down Undyne's home, and a final battle with neither able to muster any intent to harm each other. After the fact, Undyne moves to Papyrus's home.

If the player has previously killed someone, Undyne will state that she refuses to be friends with a murderer.

True Pacifist Route
After becoming "besties," Undyne gives "Undyne's Letter" to the protagonist to be delivered to Alphys after the fight with Mettaton EX (and completed the neutral route playthrough). Frisk gives Alphys the letter, which she mistakenly believes is from Frisk. They end up going on a date in the Garbage Dump where they encounter Undyne. When they meet, Alphys talks about her romantic interest in Undyne, and they reconcile emotionally.

Undyne is next seen immediately before the final boss, where she demands that Frisk and Asgore cannot fight, as she likes both of them too much. She sees Alphys there as well, and they almost kiss, from the beckoning of Mettaton, but Toriel stops it from happening, as this is all occurring in front of Frisk.

In the Epilogue, after Papyrus runs off and Sans claims to be going to check on him (while walking in the opposite direction), Undyne runs off to truly check on the air-headed skeleton.

In the credits, Undyne is seen kissing Alphys, who faints.

Genocide Route
After being bothered by the Monster Kid, the player attacks them, but Undyne weathers the blow in their stead. She is killed instantly, but thanks to her incredible Determination, she reforms in a new and improved suit of armor as Undyne the Undying, as well as having a spear through her covered eye that fades in and out throughout the battle. After being defeated, she declares that she is disappointed in herself for not being able to defeat you, but finds comfort in knowing that Alphys has evacuated the rest of the monsters to safety. She begins melting, shortly before bursting into dust due to her determination.

In Battle
She is a weapon-based opponent, mainly dealing with spears in combat. When mortally wounded by the player, Undyne manages to hang on through Determination, but eventually melts. (In a Genocide run, the lethal wound is received before the battle even begins.) This is consistent with Alphys' experiments in injecting Determination into monsters, although Undyne is the only known case of a monster with innate Determination.

Neutral / True Pacifist Route
She throws arrows from all sides at the player in Green Mode, including specifically slow and fast moving arrows, as well as arrows that flip the orientation that they are approaching from. She also launches spears in straight lines at the player in Red Mode.

To spare Undyne, flee from her while in Red Mode (it is not possible to escape in Green Mode) and run through the cave she was guarding. She'll chase you down and moves very fast, requiring two more volleys to escape from, each one harder than the last.

Fleeing from her makes the battle significantly easier than trying to weather all of her volleys in one go, as she progressively increases her projectile speed over the course of the battle, but every time you flee, the speed resets. After you complete 3 green phases, she will begin each new battle in Red Mode allowing you to immediately escape. You can also escape back the way you came from, although it takes 2 battles to do so. Doing this will allow you to heal using a save point before doing her 3rd volley.

If you don't escape while Red, she can restrict the Bullet Board to a very small box which launches spears upwards toward the player in three columns, and she also throws a volley of continuous spears at the player on a larger Board.

Genocide Route
In Red mode, she can throw rings of spears which enclose on the player while rotating, which is exclusive to the Genocide route. In Green Mode, she can conduct the same battle method as in the Neutral or True Pacifist route, only faster paced.

Quotes

 * En guarde!
 * As long as you're GREEN you CAN'T ESCAPE ! Unless you learn to face danger head-on ... You won't last a SECOND against ME!
 * Not bad! Then how about THIS!?
 * For years, we've dreamed of a happy ending...
 * And now, sunlight is just within our reach!
 * I won't let you snatch it away from us!
 * NGAHHH! Enough warming up!
 * Mercy! Ha! I still can't believe YOU want to spare ME! [Spare after Undyne reenables red mode]]
 * But even if I spared YOU...
 * No human has EVER made it past ASGORE !
 * Honestly, killing you now is an act of mercy...!
 * So STOP being so damn resilient!
 * What the hell are humans made out of!?
 * Anyone else would be DEAD by now!
 * Alphys told me humans were determined...
 * I see now what she meant by that!
 * But I'm determined, too!
 * Determined to end this RIGHT NOW!
 * ... RIGHT NOW!
 * ... RIGHT... ... ... NOW!!
 * Ha... Ha...
 * NGAHHH!!! DIE ALREADY, YOU LITTLE BRAT!
 * I WILL NEVER TAKE MERCY FROM THE LIKES OF YOU!
 * YOU! WILL! NEVER! SPARE! ME!
 * YOU'RE GETTING IN MY WAY! [Undyne's HP is low]
 * I WILL NOT BE DEFEATED! [Undyne's HP is low]
 * Come on, is that all you've got!? [After Undyne's health reaches 0]
 * ... pathetic. [After Undyne's health reaches 0]
 * You're going to have to try harder than that! [After Undyne's health reaches 0]
 * S-see how strong we are when we believe in ourselves? [After Undyne's health reaches 0]
 * H...heh... [After Undyne's health reaches 0]
 * Had enough yet? [After Undyne's health reaches 0]
 * ...I won't... ...Give up... [After Undyne's health reaches 0]
 * Ha... ha...
 * ...Alphys...Undying21.png
 * This is what I was afraid of...
 * This is why I never told you...
 * No... No!
 * Not yet!
 * I won't die!
 * NGAHHHHHHHH!!
 * I WON'T DIE!
 * COME BACK HERE, YOU LITTLE PUNK!! [Undyne catching up to you first time]
 * STOP RUNNING AWAY!!! [Second time and up]
 * COME BACK HERE, YOU LITTLE PUNK!! [Undyne catching up to you first time]
 * STOP RUNNING AWAY!!! [Second time and up]

Flavor Text

 * The heroine that NEVER gives up. [Check]
 * Undyne attacks! [Encounter]
 * Undyne flips her spear impatiently. [Neutral]
 * Undyne points heroically towards the sky. [Neutral]
 * Undyne flashes a menacing smile. [Neutral]
 * Undyne draws her finger across her neck. [Neutral]
 * Undyne bounces impatiently. [Neutral]
 * Undyne suplexes a large boulder, just because she can. [Neutral]
 * Undyne thinks of her friends and pounds the ground with her fists. [Neutral]
 * Smells like sushi. [Neutral]
 * Undyne is hyperventilating. [Neutral, late in the fight]
 * Undyne is smashing spears on the ground. [Neutral, late in the fight]
 * Undyne towers threateningly. [Neutral, late in the fight]
 * Undyne holds her fist in front of her and shakes her hand. [Neutral, late in the fight]
 * Undyne's eyes dart around to see if this is a prank. [Neutral, late in the fight]
 * Smells like angry fish. [Neutral, late in the fight]
 * You told Undyne you didn't want to fight. But nothing happened. [Plead]
 * You told Undyne you just want to be friends. She remembers someone... Her attacks became a little less extreme. [Plead if Undyne has been befriended in a previous run]
 * You tell Undyne her attacks are too easy. The bullets get faster. [Challenge, lowest speed]
 * You tell Undyne her attacks are too easy. The bullets get unfair. [Challenge, higher speed]
 * You tell Undyne her attacks are too easy. She doesn't care. [Challenge, highest speed]
 * Water rushes around you. [Undyne's HP is low]
 * Flower pollen drifts in front of you. [Undyne's HP is low]
 * The wind is howling... [Undyne's HP is low]
 * The spears pause for a moment. [Undyne's HP is low]
 * Undyne looks determined. [After Undyne's health reaches 0]
 * Undyne is smiling as if nothing is wrong. [After Undyne's health reaches 0]
 * Undyne's body is wavering. [After Undyne's health reaches 0]
 * Undyne's body is losing its shape. [After Undyne's health reaches 0]
 * Undyne's body... [After Undyne's health reaches 0]
 * ... [After Undyne's health reaches 0]

Alphys
Alphys and Undyne have mutual crushes on each other. Undyne first met Alphys in the Garbage Dump, listening for hours about where she thought the abyss there led. The two became close friends soon after, with Alphys introducing her to anime at some point. In the True Pacifist Route ending, they nearly kiss, but are interrupted by Toriel, telling them not to do it in front of the young Frisk. However, in the credits Undyne can be seen giving Alphys a kiss on her cheek.

Papyrus
Undyne thinks of Papyrus as a close friend. She is impressed by his persistence and trains him in cooking, but is concerned for his well-being and secretly does not want him to join the Royal Guard, because she believes that he is too nice to fight - even befriending the player when he was to capture them. She teaches him how to cook in hopes for a change of mind.

The Player
Undyne has a strong desire to capture the player at first, engaging them in battle and a long chase. Ultimately, in the Neutral Route / True Pacifist Route, arriving in Hotland causes her to faint from the heat combined with the warmth of her armor. This gives the player the option to give her some water.

Later on, Papyrus attempts to make them friends. Undyne resolves to befriend the player out of spite, but transitions to genuine friendship after realizing the player's fundamentally good intentions.

Asgore
Undyne sees him as more of a friend than a King. He visits her with some frequency, as Undyne knows his favorite type of tea. Being the hot-headed child she was, she once challenged Asgore to a fight. When she failed to land a single blow on him, Asgore invited her to train with him personally, eventually leading to her current position as head of the Royal Guard. In her earlier years of training, she knocked him to the ground for the first time and felt bad about it, but Asgore simply praised her for her success. She believes that he is the key to saving all Monsters.

Napstablook
They live in the same neighbourhood. They're intimidated by her (the wrestling invitation didn't help) but she tries to be a good neighbour to them. She seems concerned about them being alone after their cousin left, and tells the player to be nice to them.

Mettaton
Undyne was aware of Mettaton when he was neighbour to Napstablook, though she only knew him as Napstablook's cousin and didn't even remember his name. She is not aware that Napstablook's cousin and Mettaton are the same person. She says that "Alphys's friend" once came over to her place and lay on the piano while feeding himself grapes; this was probably Mettaton. She doesn't care for Mettaton as a celebrity, and says he gives her bad vibes.

Shyren
Undyne used to give her piano lessons, but one day she stopped coming – probably after her sister fell down.

Trivia

 * In her Neutral/Pacifist Route battle, if the player intentionally fails to block her first volley, she will repeat the same pattern for a total of four turns after which she will start using faster attacks. She explains that she wants to make the fight "fair" by instructing the player on how to block her attacks, but eventually grows irritated as she is not their "freaking kindergarten teacher".
 * If the player calls Undyne while at the "WELCOME TO HOTLAND" sign, Undyne says that she intentionally stopped chasing the player because they had a phone call. In the chase sequence, if the player is far enough from Undyne when they receive the call, she will continue toward the player before abruptly stopping a few feet away.
 * Her improved armor in the Genocide Route bears a very strong resemblance to both Mettaton NEO, Papyrus's Jogboy outfit, and Asriel's final form. This appears to be a common theme among any monster that manages to acquire determination.
 * Many have theorized that her combat style (and Genocide appearance) is based on Dragonslayer Ornstein, a boss from Dark Souls.
 * Her name is derived from the Greek water elementals or water nymphs called "Undines".
 * This is ironic, as undines are known as not having souls, while Undyne's soul is one of the strongest in the game due to her high Determination.
 * Her name also doubles as a pun on the word "Undying".
 * When Undyne was younger, she followed Gerson around to watch him beat up bad guys, much like how Monster Kid followed Undyne. However, whenever Undyne tried to help Gerson fight bad guys, she ends up attacking "the mailman or something like that".
 * If you type "Undyne" for the character's name, the response becomes "Get your OWN name!" and prevents you from using the name.
 * Throwing away the letter you get from her, then talking to her again will give you "Undyne Letter EX", which cannot be thrown away.
 * She is StrongFish91 on UnderNet.
 * According to one of the Neutral Ends, Undyne can bench press seven children. This is probably accurate as she'll suplex large boulders casually if she wants to.
 * On a second run of the game if you've befriended Undyne previously she'll say that she "remembers" you as a friend and you're a bad person who just manipulates people into liking you.
 * During the faux battle sequence you have with Undyne she says that you remind her of someone who she used to train with. This could be a possible reference to Asgore Dreemurr.
 * Undyne appears to be much calmer in their first encounters in the game, unlike the violent and crude behavior she is in later; she may only act this way as to not harm Monster Kid.
 * If you have killed all canine members of the Royal Guard in Snowdin, Undyne will comment on it, saying that the "Snowdin Canine Unit has been completely decimated".