So I was just thinking about this early image of Limbus' chapter select and how Faust's chapter is last which, don't get me wrong, does make sense. She seems to be the most important to the overall story.
BUT. Something did hit me while thinking about it. In Faust's EGO, the room is white
Like. Entirely white. We see in Canto 4 and Leviathan that N. Corp's buildings are ALSO almost entirely white. This got me thinking.
What if Faust's equivalent to a "Deal with the Devil" is a deal she made with N. Corp to gain the knowledge to make Mephistophiles, and Faust's chapter will involve us finding out what her side of the deal was, and perhaps even betraying us. This could perhaps even come with a reveal that Faust, and Limbus as a whole, doesn't have a way to bring Garnet back. Who knows how that may go.
I know this doesn't add much BUT
Both Lobotomy Corp and Library of Ruina [spoilers for those that haven't played] end with important characters betraying us. [Angela and Roland respectfully].