Oh snap, elemental cultists? And they're wrecking things up with their evil elemental ways! Well, nothing to do but get an adventuring party together and save the world. Or maybe just Mulmaster. Depends if we're going from a book or module. Either way, everything changed when the fire cultists attacked.
The dead are staying dead. In most cases, that would be a good thing, but in this case, it means something is stopping revival magic from working. What's worse, those who have once come back from the dead are slowly losing their health, wasting away by the day.
The answer to this "death curse" lies somewhere in Chult, and you've been sent to find it. The only problem is, you have no idea where to go, and Chult is a very big place, filled with dinosaurs, zombies, and zombie dinosaurs.
Welcome to Chult, hope you survive the experience.