(EDIT : So I can actually label anything I make for it, I'll call this AU "The Underground Network". It's a bit generic but it gets to the point.)
If you're wondering, this "megalovania" is an idea I had a few days ago for an AU I might not really work on, but I really wanted to make this for said AU.
The AU is based on Undercards (https://undercards.net/ , Undercards is a Heartstone clone for, well, Undertale, it's pretty fun and free.) to a degree-- At least, the battle system is based on it.
The Underground is the name of a virtual reality network where players from all over the world can join in and play a card game together, taking on Avatars to represent them. (The avatars being the Undertale characters.)
Unfortunately, due to an unknown issue, anyone who enters this place ends up stuck there with no way out. People have been stuck for a very long while in this place.
Frisk is a curious player who was not aware of the game being unable to escape from, and their "Avatar" ends up being Chara.
Sans, or at least, the player behind Sans, is in fact a Moderator for the game, but who is (mostly) deprived of their abilities due to the malfunctions from the game.
The way genocide work, the virtual reality game works on neural feedback-- If you're being particularly violent and keep attacking someone, the User behind the Avatar can eventually legitimately get killed from neural feedback.
That's the gist of it-- This Megalovania is slower paced because the battle system is a card game.
I'm not sure if I'm actually going to do anything with this AU, though, and I don't even have a name for it. Hope you enjoy the song regardless.