This information is based on alternate scenes or materials, and is not considered canon within the overall plot of the AU.
This article contains art that has not been correctly credited or hasn't been credited to the main artist. Credit the original creator of the piece or face having them removed.
Error Undyne is the head of an Error Guard in the Anti-Void.
There is no explanation yet that We could find on how Undyne became Error!Undyne. Error!Undyne takes refuge in the void and is very aware of Error!Papyrus's existence. At first Error!Undyne wants Error!Sans to stop going to different AU's and stay in the void with her and Error!Papyrus, but then later decides to destroy an AU. The AU she goes to is most likely Underfell or Horrortale, due to the comment about seeing other versions of Sans with a glowing red eye.
LoverOfPiggies has yet to explain how Error!Undyne became an error. She did however write a blog on tumblr describing the aftermath of Ask Error!Sans which involves Error!Undyne. It was said that Error!Undyne saw Error!Sans with his glasses on (which were most likely one of Alphys's pairs given to him) which put her on a murderous rampage across the multiverse. CORE!Frisk tried having all of the Omega Timeline fight Error!Undyne but with no avail. CORE!Frisk made a deal with Error!Sans to have him fight Error!Undyne and he excepted mostly because her existence alone angered him. They fought and Error!Sans killed Error!Undyne.
To Be Added...
Error!Undyne was described by LoverOfPiggies as a far bigger threat than Error!Sans. Error!Sans was described also by her as a "manbaby" while Error!Undyne was a completely insane being only wanting to brutally murder everyone in her sight. Error!Undyne, however, appears to have a remaining soft spot for Alphys as she got set off by Error!Sans wearing her glasses.
Error!Undyne has the same powers as Undyne from Undertale, but has some new powers, such as ripping holes in the multiverse, teleporting and body distortion.
She is friends with Error Papyrus as far as we know, (according to the ask!error) and she also once stoped Error Papyrus from going into Underswap and making friends with Swap Papyrus.
- Error!Undyne is very close to Error!Sans in power.
- Error!Undyne original wanted to team up with Error!Sans.
- Error!Undyne is stronger than Undyne the undying.