Adgharhin Way/Book of Lyonniths Helm

The Book of Lyonniths Helm was recently found by Nicholas of Arcachon. It was identified by the writing style on the cover; the apparent age of the book, and the title.

It also has the mysterious quality of being unopenable:

The book remained closed as if it were made of a solid slab of rock. [Nicholas] also demonstrated that a thin object like a piece of parchment or knife blade could be slid into the book between its pages, but could not be used to pry it open.

It is believed that the book can be opened after voicing a certain prayer written in another book (like the Book of Relics).