* The following article or section has content which has neither been confirmed nor denied as canon by creator.
Error Undyne is the head of an Error Guard in the Anti-Void.
There is no explanation yet that I 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.
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.