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– Undyne before her battle

Undyne fills the Captain of the Guard role in Undertale.



Undyne prepares to throw her spear at the protagonist.

Undyne debuts in armor varying in light and dark shades of gray, but without armor, is a piscine, anthropomorphic monster. She has blue scales and a long red ponytail. She has red and blue fins on the sides of her head, and a pair of sharp, yellow, protruding teeth. She wears red eye shadow and has an eyepatch on her left eye. She also wears a black tanktop and jeans. Her eyes have black vertical pupils and a yellow sclera. Undyne has no nose.

Alphys DateEdit

During the date with Alphys, Undyne wears a white turtleneck under a black leather jacket, pants, a light-colored eyepatch, and lets some of her hair down.


Whenever she persists through Determination after her HP reduces to zero, her pupils turn white, and her sclera turns black. She no longer has an eyepatch, and her newly revealed empty eye socket emits a flashing light that looks like a spear. Her hair spikes at the ends and her fins become more rigid and pointy. She also appears to have donned a new set of darker colored armour with souls/hearts on her chestplate and on her new white gloves, accompanied by boots with pointed toes.


Undyne is passionate about everything that she does. She acts quickly on her ideas and is steadfast in her beliefs. Though she wants to defeat the protagonist, she also tries to be fair and offers an explanation of how Green Mode works. Asgore taught her the value of pacifism, which is why Undyne sees the protagonist as "a wimpy loser with a big heart." When the protagonist first encounters her, she fights to further Asgore's plan of collecting seven human SOULs but, if the protagonist shows mercy, Undyne just as quickly defends them from Asgore.

She loves to help others and mentors Shyren and Papyrus in various skills. Undyne dislikes puzzles, loves japes, and enjoys anime, an affinity she shares with her romantic interest, Alphys. Since Alphys told Undyne that anime is actually human history, Undyne regards human history as exciting and cool.

Out of all encountered monsters, Undyne possesses the most Determination. She melts before her death, implying that her body cannot handle the amount of Determination she has.

AU's Undyne is in Edit

Relationships Edit

Alphys Edit

Undyne has a crush on Alphys which flurishes into a full relationship on a pacifist run.

Asgore Edit

The king of monsters is Undyne's friend, boss and trainer.

Papyrus Edit

She is Papyrus's friend and trainer. She also teaches cooking despite sucking at it herself.

Sans Edit

Undyne is Sans's boss, she never refers to him by name.

Napstablook Edit

He is Undyne's neighbour. They don't know each other well.

Shyren Edit

She had taught Shyren piano lessions prior to Shyren's sister falling down.

Monster Kid Edit

MK idolises Undyne.

The Royal Guard Edit

Undyne is the captain of the guard. She cares about the members and is assumed to know (most of) them fairly well.