I created a Miniverse once. Mini in that it only provided the afterlife/multiverse of a single culture. For my Kaidan setting of Japanese Horror, I created a reincarnation cycle emulating the Buddhist reincarnation cycle which was overlayed onto the Social caste system. Where each social caste comprised one of the "hells', which all the destinations on the Buddhist reincarnation cycle are considered "hells". There is one true Hell, home of the Oni and Akuma, lorded over by Emma-O, an evil god. The other five planes of existence that coexist with the social caste system are comprised of Heaven (Kaidan aristocracy), Asuras (Buke or Samurai caste), Human (Commoner caste), Animal (Obake/Yokai), Hungry Ghost (Hinin/Eta oppressed caste), and Hell... There is also one more plane of existence needed, that sits outside the social caste system/reincarnation cycle and that is Yomi (the land of dead, where spirits go at the moment of death). That's the entire Mini-verse for Kaidan.