When you're a GM, coming up with everything in the game world that's not the PCs is your job. And, sure, you can create an entire menagerie of monsters from scratch, but why when there's resources to help you out? That's where Pathfinder Bestiary 2: Iary Harder *gets a note* ... apparently, "Iary Harder" isn't a thing. It's just Pathfinder Bestiary 2. Anyway, that's where it comes in. Get a look inside in this preview.
From the article:
More than 300 menacing monsters and fearsome foes await within a compendium of creatures from the world of Pathfinder! From classic adversaries like giants, dragons, and the jabberwock to potential allies and servants suitable for summoners of every alignment, this must-have expansion to the Pathfinder Bestiary seethes with enemies to challenge characters of any level.