Episode 1 : Where everything went wrong

This is a project I hold dear to my heart. A story I began conceiving shortly after joining the Undertale fandom, a few years ago. And today, after setting it up for more than 12 months now, I think it's finally time to start working on the main thing. Will I be able to make it all work out ? Will it be appreciated ? Only the future can tell. When the dark side of the multiverse unites in a dangerous common cause, the future of all AUs has never been more uncertain... Could this truly be the end of the Underverse ?