A strange book talked about at the Inn

A few dwarves discovered a flesh covered book writen in Abyssal in the mines....

It refered to a being called the Prince of the Lower Aerial Kingdoms. He rules the skies above all layers of the Abyss. One of the oldest and most reprehensible demon lords, Pazuzu is a master manipulator and corruptor of mortal souls. The Dark Angel of the Four Winds takes great delight in offering aid that seems beneficial, but which in fact leads to great evil and suffering. Unlike most other demon lords, this one is able to manifest freely in the mortal world. Over millennia, he has perfected the craft of seducing mortals to his will without attracting the attention of the gods that protect them. Unlike most demon lords, he is not interested in conquest of the Abyss. His main concern is winning followers on the Prime Material Plane by tempting or deceiving those of good alignment.

Celovar the Elf and Arya were last seen in possession of the book.