From the title page:
A GAMMA WORLD ADVENTURE FOR PAX PRIME 2010
This is Gamma Terra, the synthesis of uncountable realities collapsed into one by human error. Mutants, robots, and space aliens all roam the wasteland that once was Earth. (Well, many earths. Well, many planetesque things called various names but vaguely resembling what we perceive as Earth.)
A castoff from a destroyed planet in the weirdest reaches of space, the meteorite of earth and vegetation crashed in a shattered city near the coast of the Pacific Ocean. Misguided creatures from a technology-free reality, the gren, came to worship the creature and to call it the Returned Earth. The lump of sentient rock won’t be satisfied until it has obliterated all technology by sending a destructive signal through a large metal spire within the city. A patrol comes to capture the characters and drain their blood to nourish the Returned Earth (it’s complicated). Can these mutants survive the initial attack? Will they strike back at the Returned Earth? Is life even worth living if they don’t have their technology?