From the introduction:
The entire party of adventures is dead! Whether from bad luck, poor planning, or just being at the wrong place at the wrong time, the dice failed them for the last time. Lucky for them, the gods have intervened to offer them one more chance.
This adventure is for a party of any size and any level. It takes place after a TPK (total party kill) event. It draws heavily from the Fires of Dis, although access to that book is not required. The entire adventure plays out on Averuns, the first of the nine Hells of Baator.