“Even if I’m alone, night will come. And every night is followed by dawn... A mere star that will fade cannot hope to best the light of the rising sun. Be prepared; For today, a Star of the City shall be gone.”

You are the librarian of Kether floor and as Xiao says this phrase you find yourself on the battlefield, again, but this time she manifested EGO, and she's determined to get the Book of Lowell. She won't stop until becoming book as well or getting her revenge.