From publisher blurb:
For centuries, adventurers have been finding Blackdyrge's Bestiaries within the treasure hoards of terrible monsters. These volumes include rigorous details about the lairs, habits, and of course, treasures, of some of the most powerful monsters in the world. Their value to adventurers is incalculable, despite the fact that they often lead the foolhardy to an ugly, and often painful demise.
Dozens of Blackdyrge's Bestiaries have been discovered, yet nothing is known about the author himself - until now. The history and whereabouts of the mysterious sage of monsters is revealed in this free download.
Blackdyrge's Bestiary: About the Author contains 8 pages of new d20 material, which includes:
A full, revised stat block for Blackdyrge himself
The twisted tale of the dread sage's history and origins
A new magic item: the dread Blackdyrge's Bestiaries