The name Forbidden Scrollery makes me think of Byakuren, for obvious reasons. Perhaps it will somehow involve her, or even be about her. Like, her past with her brother or what she had done in Makai along with her ventures including the Myouren Crew. Maybe Shinki will appear!?!?! Doubtful.
I do have a slight belief Byakuren will somehow be involved. I don't think it will have anything else to do with what I said, but it's a possibility Byakuren is at least involved. Like others have said, a new character will be introduced, likely as the main character. Whatever the case, I'm looking forward to it! Comes out around the same time as the Dark Souls DLC. That will be a FANTASTIC week~