The guide says:
Black Magic Alternate Endings
In Chapter Eleven, Black Magic may either show up to help or hurt you depending on your choices and relationship stat. If Black Magic is your enemy, you can unlock a Black Magic de-powered alternate ending choice OR choose a game-ending alternate ending where you and Prodigal end the world. You can also choose to end the world with Black Magic as an ally.
How exactly would I get the emphasized part (ending the world with Prodigal)?
In my playthrough, I broke up with Black Magic and romanced Prodigal. Then during the ending I got the choice to attack Black Magic with all my power. And when I did, the “normal” Black Magic alternate ending happened (with me and Black Magic alone, the same as when you’re romancing her and choose to give her all your power).
Is this what the guide meant? Or is there some other ending for Prodigal? How can I get that?