[[Archbishop]] [[Lazarus]] is usually accredited to have written this [[Tome]]. He was as far as anyone know the only real "[[cultist]]" of Diablo at the time it's presumed to have been written. The other thing is that [[The Realms Beyond]], [[Tale of the Three]] and [[The Black King]] are written with the same style, and the latter mentions things that undeniably has to make the writer Lazarus.