It says: "Building a small shrine does not equate to a full temple, but it serves as a reminder to the local followers. Shrines strengthen the faith and will provide a gathering point for the believers.", but what does it mean?
When I enter the temple I get information: "This temple can provide for ca. 17500 followers." so it is exact information.
How many believers shrine can support (if any)?
Also there is temple treasury.
Temples are upkeeping from there.
There is no thing like shrine treasury so how to upkeep shrines in region without temple and when they draw from global treasury the region lose believers rapidly.
So generally, shrines can be payed only in regions with temples (where they are not needed) and in regions without temples they only cause rapid lose of believers.
So, again to return to my original question: what is exact use of shrines?
