The Book of Destiny and the Pen of Judgment are a match made in heaven.
The Book of Destiny was the Nen ability of Rem Nostrade. After his death, it manifested and remained as a Nen item, yet only his direct bloodline descendants who possessed the exact same talent were qualified to inherit it.
Le Eifu, upon acquiring the Book of Destiny, further developed it and made it her own, integrating it completely so that it became her personal Nen ability—though she rarely used it, fearing it would stir up painful memories.
Chapter 221