The party may have accidentally caused severe damage to the fabric of reality, letting a devil release hordes of soul eaters into one of the planes of the afterlife. They're not hard to kill, and when they run out of nearby ghosts they start eating each other. Shouldn't be too- Wait a minute. This part of the afterlife is a featureless white desert where it's always night...
The Necropolis is a fortress filled with psychopomps and dead adventurers, and Inari can now cast Giga Slave or something, so fighting them off wasn't much trouble.
Oh, and Alveri's real name is- *shot*