Like the core rules set, this box is mostly empty, with a rule book, small set of cards and maps & counters. The rule book adds several new Origins, including AI, Alien, Arachnoid, Cryokinetic, Ectoplasmic, Entropic, Exploding, Fungoid, Gelatinous, Magnetic, Mythic, Nightmare, Plaguebearer, Plastic, Prescient, Reanimated, Shapeshifter, Simian, Temporal and Wheeled.
The book also re-introduces the Cryptic Alliances, the "powers" of Gamma World. Some like the Resorationists and Archivists seek to "fix" the world, but others like the Knights of Genetic Purity and Red Death seek to conquer it. The cards included in this box allow you an ability based on your membership in a Cryptic Alliance.
Next we have a bunch of Mutant Creatures including a few classic Gamma World mutants like Arks (dog folk), Carrins (age vultures) and mounts like Brutoz, Podogd and Jackalopes. A few D&D monsters also appear in this book; CIFAL, Froghemoth and Garbugs.
The remainder of the book is an adventure and guide to the surrounding area. Unfortunately, the adventure is presented in "4e format" where the adventure and the encounters are in separate chapters which requires far too much page flipping and backtracking to run the adventure efficiently.
One thing that is not in this box is new Alpha Mutations and Omega Tech. Since these are limited to cards only, there are none included in the expansion. And for those hoping for a list from the last set, sorry not here.
Much like the start up box set, this could have been the best version of Gamma World if they had just put a little effort into it. Why not just include some blank cards to players can create their own mutations and tech? Or just a list of abilities so the Game Master knows what to expect? As with the previous box, this will take some work to be a functional RPG, but it might be OK for a "one nighter" game session.