The Great Church

The Great Church is the only official religion in Arcesia. Any secessioned groups. like the Greater Church and the Greates Church, are led by evil heathens without any moral qualms. Their church wardens only try to enrich themselves, not caring that they will lead your soul to eternal suffering. Of course, they say exactly the same about the Great Church. 
Unofficially, there is tentative cooperation in some remote areas. In other areas, any heathen will be chased out of town, covered in tar and feathers. If she's lucky. 
Due to the sparse population of the land, there is no all out war. However, a traveller would be wise not to menstion the church they belong to, unless she's sure it's the right one. Saying you do not believe is never an option. Not even for the wise women and men, who are rumoured to dabble with the supernatural world. It is wise not to follow the person who guides you to the fairies. 
Officially, everyone is a member of the Great Church. Most people do attend regular church services. It is a way to socialize with other people.  Church officials are also economical and political leaders. Or the other way around, there is no separation of church and state. If want to become rich, church leadership is your best bet. However, the church wants the most blessed leaders. Thus they choose the richest, most connected and decently educated people. After all, it takes a lot of time to pray for the souls of the more unfortunate. Working 16 hours a day on the fields does exclude you from that, unfortunately.
Teachings The Helper and the Companion watch over you. Together they keep an eye over you, which you see in the sky at regular intervals. You are the Pupil. You are supposed to follow the guidance of the Helper and the Companion without question. The Church will interpret Their wishes and assist you with following them. Questioning the authority of the Church is not good for your soul. The Helper might not want to assist you to your afterlife if you did not help Them in your life. People who are good followers of the teachings of the Church are blessed with worldly rewards. But your main reward will await you after your death.