From the introduction:
Belly of the Beast is a grim tabletop roleplaying game about brutal, selfish scavengers surviving in the gut of a titanic, parasitic, world-eating monster.
Hundreds of years ago, a massive rock fell from the sky, crushing kingdoms and continents beneath it. Eventually, life in the realms returned to a state of normalcy, and the many clans continued their incessant struggle for power.
Three generations past, the skyrock—said to possess foul energies and discordant vibrations—erupted in a disgusting ball of effluence and viscera, revealing the creature that dwelt within it, the Swallower of Worlds, the Insatiable God, the Devourer, or simply: the Beast.
Incalculably large, the Beast unfurled its great girth upon the land, consuming thousands of leagues of soil, stone, and forest. One by one, the mighty strongholds and great armies of the age fell against its inexorable consumption.
And yet when legions, empires, and cities are swallowed whole, not all is lost. A rare few survive the Devouring, and test their mettle living in the belly of the Beast.
You are one of these exemplars of grit and greed: a scavenger. Hundreds of great civilizations have been consumed, but their wares, artifacts, and materials are ripe for the taking deep within the recesses of your new home’s guts.
Plenty are brave, desperate, foolish, or insane enough to try to make a living in this horrid place—but few survive, and even fewer thrive.