The Inner Sea Monster Codex is a 64-page entry discussing ten different monstrous races for the Pathfinder RPG. The write-up for each monster includes background on the monster in the official campaign setting of Golarion, a summary of common encounters, and full stat blocks and pictures for various members of the race. In addition, many of the races include new features like archetypes, traps, oracle curses, feats, magic items, spells, etc. The monsters covered are:
* Centaurs. Everyone knows what these are, and centaurs in Golarion follow the fantasy tradition of being stubborn and xenophobic. This section includes a new archetype for centaur cavaliers called the Charger.
* Charau-Ka. I had never heard of this type of monster before. Charau-Ka are basically primitive ape-men, violent and brutal scavengers in Golarion's jungles. This section includes several Charau-Ka traps, many of which are quite creative and would be fun to use in a game.
* Cyclops. In Golarion, cyclops have a strong diviner/oracle flavour and are seen as quite rare. New oracle curses and a Cyclopean oracle archetype, the Cyclopean Seer, is included here.
* Derros. Everyone's favourite crazy evil gnomes. I really like their portrayal here as hidden threats that lurk underneath urban areas and kidnap surface-dwellers for strange experiments before brainwashing them to forget the whole thing. It would be quite easy to get PCs involved in investigating the mystery of missing persons. Several new alchemist discoveries are added.
* Gillmen. Merfolk that have a special role in Golarion lore as descendants of the ancient Azlanti people. I assume Gillmen will get even more attention in the upcoming (at the time of this review) Ruins of Azlant adventure path. I've never done much with aquatic races, but for those interested, several Gillman magic items are included here.
* Girtablilus. Another new one for me: basically, giant scorpions with human upper bodies (think centaurs but swap giant scorpions for horses!). In Golarion, they mainly appear in desert settings and as guardians of ancient ruins. I wasn't particularly impressed, but your mileage may vary. Two new druid domains (Ruins and Vermin) are introduced here, along with a new oracle curse (Site-bound) and a Girtablilu-specific feat.
* Minotaurs. In Golarion, minotaurs are the product of the demon goddess Lamashtu, but full the stereotypical role of guarding ancient labyrinths. There wasn't anything revelatory here for me. Four new spells are introduced that all focus on creating illusions to confuse travelers.
* Ogrekin. Mutated, deformed, and disfigured freaks. One gets a "The Hills Have Eyes" vibe. I quite liked the two tables of Beneficial and Disadvantageous deformities for the ogrekin, and there's also a template for creating half-ogres.
* Strix. Very cool looking winged humanoids who live on remote mountain perches. I could definitely imagine doing something with them. Six new feats for creatures with natural wings are included here.
* Urdefhan. Creepy demon-worshipping monsters from another plane who live in the Darklands (Golarion's equivalent of the Underdark). Nightmare-fuel that's perfect for adding some horror to a session. Six new feats (Urdefhan-specific) are included.
The artwork is uniformly excellent--really, it's as good as it gets in fantasy RPGs. Although not every monstrous race presented here was my cup of tea, there's enough creativity and mechanics crunch to make the book worth purchasing if any of the creatures presented here appeal to you as a GM. Do note that this is primarily a GM's book; although some of the mechanics options (feats, spells, etc.) could be used by PCs, most have a prerequisite tied to being one of the monstrous races.