From publisher blurb:
Expanding Codex fleshes out monsters from the Creature Codex, giving GMs ways to modify the existing monsters to surprise well-prepared players or to introduce monsters to a campaign. At a full 32 pages, the Expanding Codex brings you variant monsters and magic inspired by the pages of the Creature Codex:
17 variant monsters from Creature Codex, including the swolbold, drakes, and unhatched
22 new magic items from the Periapt of Proof Against Lies to the Firesight Goggles
26 new spells including mindless vengeance and siege of iron
Plus adventure hooks, 2 feats, and a ranger companion!
Add these variant monsters to your campaign with alternate traits and actions, or outfit your characters with new spells and items inspired by the monsters. Either way, prepare for adventure, choosing from a slew of adventure hooks!