From DreyNet

Also known as the Black Book, the Midnight Apocrypha, and the Psalms of Forgotten Voices. This book contains the rules governing defunct or unfinished realities as well as the worlds themselves. It is this manuscript which is transfigured into the person of Elysia by a combination of the Wefter’s interference and Rubric Dahns’ dreamcrafting.

Mr. Teele and Mr. Krake are searching for it.