Aeron and the Wrekin Border
Religion in Treyine is complicated!
The Church of Law was brought to the island by the Tropiline Empire, but remnants of Tropiline polytheistic worship was still strong, particularly amongst the military. The native population was never completely converted and Druidism is still fairly common particularly in Mertsia, Rheged and Northumbria. In wilder lands still, Riata, Dumnonia and the Shadowed Isle, the Auld Faith is the source of worship and sacrifice. The Northmen brought their wild gods with them with paganistic practises and calls to heathen deities with their promises of Valhalla and Ragnarok. Finally, evil never sleeps. The Cults of Chaos still hold sway amongst many seeking power and wealth.
Where humanoids and beastmen have religious practices these tend to be shamanistic and often simply Cults of Chaos cloaked in a primitive mythology.