From the introduction:
Centuries ago, the four deities worshipped by mortals – Kishar, Kotaresh, Lyth, and Asar-Segt – threatened to drown the world in a flood of saltwater to punish the living for their impiety.
The oracles and witches of the realm struck a desperate bargain with the gods, however, and convinced them to spare the world. In exchange, the mortal kingdoms were bound to demonstrate their faith once every generation by sending their most courageous and adroit warriors to the Crucible, a ziggurat in the lowest valley of the land.
Every quarter-century, on the first full moon of summer, an eclipse darkens the night and the sealed ziggurat opens. Many traps, tricks, and guardians lie within the Crucible to test those who enter. Few who heed the challenge of the gods survive – most find only quick death.
If the races of the world are deserving of the gods’ affection, their champions will overcome the trials of the Crucible and light the Divine Brazier hidden in its uppermost chamber.
If they are not, the flickering candle of civilization will be snuffed. Little of value will have been lost.