Secrets of the Void

Secrets of the Void is one of the artifacts used by shadow priests in World of Warcraft: Legion. It is automatically equipped in the off hand when wielding Xal'atath, Blade of the Black Empire.

Source
This item is a quest reward from Blade in Twilight.

Trivia

 * The flavor text was changed from "Written by Natalie Seline, this book contains dark secrets given to her by the Blade and other sources." during the Legion alpha.