A mysterious nothingness called the Void Is disintegrate all of existence- Twilight goes through the usual time-travel shenanigans in order to buy the universe some more time.

There are some mentions of other shows/games/whatever, but the story isn't actually a crossover, also while humans do make an appearence, they won't appear much, so you'll be able to ignore them for most of the story.
OC's will mostly take up minor supporting roles.
I'll update the tags once i know what i'm doing.