slowly thinking about doing a #Harnmaster game again. Well, #Harnworld, which originally was an off-brand ADnD supplement. Basically one of the most well-realized examples of worldbuilding along the ideas of #DnD/ADnD.
It's just a single campaign area, and it has a whole coherent theology, history, reasons for all the classes, and weirdness. There's a mechanism to have every weird monster you want on there. And every place is described as just on the brink of interesting events.