I am the savior of all monsters!
I am the heroine they all deserve!
I am Undyne!!
It will be the last thing you will remember!
— Undyne introducing herself

Undyne is a cyborg fish monster that the protagonist first encounters at the Lab. She takes the role of Mettaton.



Initial Form

Undyne is a fish-like humanoid monster, but has parts of her body made out of metal, thus making her a cyborg. She has red and blue fins on the side of her head. She wears a black tank top with a keyhole in the shape of an upside-down arrow on it, possibly resembling a spear blade. She also wears long red boots and pants that go down past them.

Undyne Umbra

Undyne changes drastically in terms of hair and clothing. Her hair becomes longer, with a blue crescent moon hairpin. She wears a sailor fuku uniform, which consists of a white leotard with a blue collar, a skirt of the same color, and a red bow on her chest. She also wears white and blue gloves and red knee-high boots with white borders at the triangular top.


Undyne usually hung out around the Waterfall, she would go to Hotland to brawl with the "local kids" after a long cold soak.

One day, one of the kids dared to lift up the CORE and she accepted it and succeeded. However, lava splashed on her when she was setting it down.

The moment Asgore heard about what happened to her, he aided to her. Once Undyne heard about his knowledge of science, she requested to have robot enhancements. Ever since Undyne had been calling Asgore "Sensei".


  • Undyne Umbra's transformation is a blatant reference to Sailor Moon.

Main Characters BoogiePapyrusCharaAsriel DreemurrTorielAsgore DreemurrUndyneSansFriskMettacrit
Ruins Enemies DummyFroggitWhimsumMoldsmalLooxVegetoidMigospAlphys
Snowdin Enemies SnowdrakeChilldrakeIce CapGyftrotDoggo
Dogamy and DogaressaLesser Dog Greater DogJerryGlyde
Waterfall Enemies AaronMoldbyggWoshuaTemmieMad DummyShyren
Hotland Enemies VulkinTsunderplanePyropeMuffetRoyal GuardsSo Sorry
CORE Enemies Final FroggitWhimsalotAstigmatismMadjickKnight Knight
Amalgamates MemoryheadEndogenyCorinthianLemon BreadSnowdrake's Mother
Hard Mode-only enemies ParsnikMoldessaMigospel
Vendors Nice Cream GuySnowdin ShopkeeperGersonTem ShopBratty and CattyBulgy Pecs
Other Characters NPCsMonster KidvoltrathelivelyRiver PersonFallen HumansNapstablook
W.D. GasterLost Souls