In this AU, Frisk fell into the core and gained the ability to be in any Undertale timeline/Alternate Universe that she wants.
(She might even have to take this thing with her-it might be useful!)
Undertale AUs (in my opinion)
By ssenisgone
Hi! This is a random idea I came up with, and in it, I'll be listing every undertale au I know of, and (at le... More