Adding a new religion

[uanime5]

New religion
The information on which files to use was provided by Octavius. To add a new religion you need to do the following (since this is pretty straight forward I won't included diagrams).

1) Open descr_religion.txt and add you religion to the list (in this case diabolical), then assign a pip (small icon, which need to go in the ui\pips folder).
2) Open descr_religion_lookup.txt and add your religion to the religion look up.
3) Open text\religions.txt and add your religion to the list.
4) Open world\maps\base\descr_regions.txt and add your religion to the various settlements. However these setting will not take affect unless you delete the map.rwm file in the same folder (thanks to SigniferOne)

To make a faction this new religion open the desc_sm_facton.txt file and change the faction's religion to this new religion.

Religious buildings
As SigniferOne pointed out a religious building is designed to convert to a certain religion only, it does not convert to whatever your factional religion is. Below is the Catholic religious buildings, with the religion highlighted in red.

building temple_catholic
{
    convert_to temple_catholic_castle
    religion catholic
    levels small_church church abbey cathedral huge_cathedral 
    {
        small_church city requires factions { normans, denmark, hre, scotland, france, england, hungary, poland, venice, papal_states, portugal, spain, sicily, milan, } 
        {
            convert_to 0
            capability
            {
.
.
.

A new religious building needs to have the religion changed, in the example below it's changed to Latin.

building temple_latin
{
    religion latin
    levels cathedral
    {
        cathedral city requires factions { normans, denmark, hre, scotland, france, england, hungary, poland, venice, papal_states, portugal, spain, sicily, milan, venice, } 
        {
            capability
            {
                ;agent priest  0  requires factions { normans, denmark, scotland, hre, france, england, } 
                recruit_pool "Armored Clergy"  1   0.4   3  0  requires factions { denmark, } 
                happiness_bonus bonus 2
                religion_level bonus 5
                agent_limit priest 2
                pope_disapproval 1
                pope_approval 1
                population_health_bonus bonus 1
            }
            material wooden
            construction  4 
            cost  6400 
            settlement_min large_city
            upgrades
            {
            }
        }
    }
    plugins 
    {
    }
}

For more information about adding new buildings see this thread http://www.twcenter.net/forums/showthread.php?t=77577