Is it Shaker!?

Beware the rainy season on this savanna because the only wind that blows are the Winds of Change, and the only rain that falls are the Chaos Rains. Wizards, alchemists and seekers of curiosities living just beyond the borders will pay incredible sums for altered beasts and monsters transformed by the magical weather into bizarre new forms, but the characters who venture into these lands risk becoming altered themselves.

Transmutation and transformation themed hexcrawl. Learn the rhythms of the season or be transformed either in whole or in part in random ways. Seek a fortune, and maybe discover the secret that lies at the heart of this chaotic, shifting land.

Among the most depraved elite gourmets, unscrupulous wizards and debased wretches of society there is a fierce demand for a secret forbidden mushroom, one that only grows on the bodies of the undead. They're supposedly an unmatched delicacy, and rumored to let people see beyond the veil if prepared just so. While selling or possessing them is a crime, the law was willing to turn a blind eye because these fungi were so vanishingly rare that they were practically never seen.

Someone has begun to flood the market with them, in amounts that would require thousands of ghouls to produce and farm. They must be found and destroyed. Get to work.

Ancient texts refer to things called "Stars" and "The Sun and Moon" which floated above in a special cavern called "The Sky" which was supposedly so large that the ceiling and walls couldn't be found or seen no matter how far one walked or climbed. That's nonsense, like "the surface", a myth. Fools have tunneled up and up and up for their whole lives and never found any of them.

Because they aren't there anymore.

Ages ago, the entire world was suddenly, instantly covered in stone, and stone, and stone, and stone, and stone a thousand times over. Stone without end. Raw stone, massive megastructures, whole worlds worth of mountain ranges and oceans and cities and caves that could swallow nations whole. All creation in an endless underground. The gods of the sky went mad and vanished at once. The gods of the dark inherited the world.

This is where we live now, in the endless beneath, searching for remnants of the old world and ways to survive our new world.

Your hometown is built on the back of a titanic beast that roams slowly from oasis to oasis, past ruined cities that were once full of people. The party is one of several groups tasked with securing supplies, food and artifacts each time the titan stops. Occasionally other titans and other villages compete for the same resources - they have to be handled, either through negotiation or battle.