It is complicated as I am still working it out but I can outline the first bits. I am currently separating it from the various attempts I have tried with Nomadic Start.
When you get the tech Animism
- your regional form of Animism will spread to all your cities. For example Animism - African if you have base Culture of African. It has no holy city or shrine. The only buildings it has are Lesser Shrines. Each city can have three Lesser Shrines based on local conditions one each for
- food plant
- domesticated animal
- land form or wild animal
- The plant and domesticated animal will provide a small boost to
, the land form a small boost to 
and the wild animal a small boost to military, non-military units or 
.
- The Religious Form civic allows you to choose between Religious and Atheist. Religious doubles the boost of each shrine. Atheist adds either a or education boost depending on the individual shrine.
- Based on the Cultures you have you may build a specific religion for example San(Animist) or San (Atheist). This will give you a Holy City and the religion will automatically spread to all your cities without a period of anarchy. You will only be able to build one of these. It allows you to build temple level buildings. This allows a second set of lesser shrines.
- Nations with the same Animism - Region get a +1 attitude towards others with the same Religious Form.
No matter which Religious Form you have you will be able to build the "Faces of God" mod
Religious Way buildings. Which ones are available to you will depend on your tech level and the piety level of your religion. Piety level is based solely on the number of buildings of that religion active in the world.
Pantheism will become available at a tech in the Prehistoric Era. The Elemental buildings (air, fire, stone, etc.) may have a religious component.
At Polytheism you will be able to convert to a Polytheistic religion by building the "Unify the Pantheon" national wonder building. This will allow you to choose from the available polytheistic religions, ie those not yet founded and you have the tech for. For example San(Polytheistic). Where you build the national wonder will be where the holy city is. I am currently thinking that the Shrine buildings will replace the national wonder so that if you like you can found another religion but it wont be able to be done in the same city.
- While you don't have to convert to Polytheism and the new religion if you do so when you build the wonder there will be no anarchy and the religion will spread to all your cities. There will be extra but reducing unhappiness in all cities but no anarchy. Leave it to later and you will need to spread the religion yourself.
- Each lesser shrine increases the cost of the national wonder slightly since there is more to do.
At Monotheism you will need a Great Person to change to the Monotheist civic and choose a Monotheist Religion. For example San(Monotheistic).
Religious Tenets.
These are like civics and affect your nation in cities that have that religion.
Only the owner of the Holy Shrine can change these except when the Council of the religion is built. The Council can only be built by a nation that does not have the Shrine. Once built changes to the Tenets are voted on (similar to UN) with the number of your votes determines by the buildings in your nation.
- Proselytize verses non-proselytize
- Focus on god verses focus on the flock verses focus on self enlightenment
This will probably be split further and defines the basic bonuses that temples and cathedrals give.
- training of priests - inspired; master/student; ordained and so on
Sorry that is all I have time for now. I have included a number of Praetyre's ideas in the details. This is more by way of an overview.
. Canaanism spreads slowest of all. In that particular case I think it is a bug.
