The civilization that has the most territory and largest population. Though scattered across the ocean of the inner world. Only a handful of large cities and the rest of the population is spread across the thousands of islands of all sizes in the ocean. Every single island has at least a church (though many get abandoned or forgotten)
They worship a strong but indistinct pantheon of gods. Angels can be found everywhere across the ocean. Slavery is legal and everyone is owned by someone else with the church owning the highest levels of society and the gods owning the church. Everyone in their place, everyone does their duty. One can improve their place, but with the gods (and angels) providing protection and comfort there isn't much ambition to succeed in most people who live there.
The people of the Ivory Dominion are some of the healthiest in the entire underworld. Plenty of actual food from the barely changed surface world plants and even non-lizard livestock for meat. Actual cow-meat is a luxury export. However, people who have grown up in the inner world react very poorly in the underworld proper. Claustrophobia (known only as the crazy dementia of the inner world), shakes and sickness from lack of sun, fear of the dark (more than rational fear anyway), and countless other problems.
Known specialties: Sun magic, boats, statues, healthy slaves,