In ancient days, when The Masters ruled in their obsidian cities and created great and terrible monsters and machines, humans were just the least of their creations, fit only to bear cups and clean up after their rulers. But then The Masters vanished, and their floating cities crashed into the ocean. Along with elves and goblins, dragons and demons, humans were left to struggle for supremacy. Some abandoned the leavings of The Masters and splintered off, forming barbarian tribes that warred with each other and the mutants of the wastes. Others formed colleges of wizards to study The Master's magic, in hopes of claiming that awesome power for themselves. With no Gods left to serve, some creatures sought out new ones, and in doing so their churches became locked in an unfathomable struggle of holy versus unholy.
And amidst it all, the ruins of the masters lied untended, waiting to be plucked by anyone who would seize them. Entering a dungeon is illegal. Tampering with magical seals and ancient machines could bring peril to those nearby, or even the entire world. But the administrators of townships and city-states have no real power in the face of ruthless Thieves Guilds, barbarian warlords, and churches determined to root out the unholy at its source. And so, for coin, for power, and for glory, the delvers enter into the unknown.