Dominion represents your pretender's religious influence over a province and the degree to which its inhabitants worship them. Note, conquering provinces does not itself expand your dominion. Military control of a province and religious belief are two different things. Your armies can march across entire continents without changing the dominion in the provinces they’ve conquered, while the influence of your god can spread beyond your borders.
Dominion in a province is measured in candles. Only one god can have dominion in province at a time. The maximum amount of candles a god can have in a single province is limited by the dominion score selected when creating that pretender. This number will increase by one for every 5 temples you build (or 5 per player on the team in a disciples game).
Dominion can be generated from several sources. Primarily it is generated by your pretender, your capital, your temples, your prophet and any thrones of ascension you have claimed as your own. The chance of dominion increasing from one of these sources is [50% + 5% * maximum dominion], up from [10% * maximum dominion] in Dominions 4. For example if your pretender was built with a dominion score of 8, and you have five temples your maximum dominion is nine and each source will have a 95% chance of generating more dominion every turn. For your pretender, he/she/it will always generate one point of dominion and then has two chances (using the previously mentioned %) at generating additional candles. Thrones will get a chance per level of dominion on that specific throne (1 to 7 depending on the throne). These percent checks are referred to in the game documentation as 'temple checks' (regardless of actual source being a temple).
When a new candle is generated (a temple check occurs) the following process happens:
It is more difficult for dominion to spread from land→sea or from sea→land province. During the third bullet above if the randomly selected province crosses the land/sea border there is a 50% chance that another province will be selected instead.
This sort of dominion spread happens late in the turn – notably, after combat.
Dominions can also be increased in a province by having your priest units preach. A preaching commander has a chance to increase your dominion in their current province, even beyond your maximum dominions. The chance of success is 30% * your priest's level. Any candles generated by this cannot spread to adjacent provinces. Having a friendly temple in the province adds 0.5 levels to your priest for the purposes of preaching. (So a level 2 priest with a temple would have a 75% chance of success) If you are preaching in a province with enemy dominion, the chance is then decreased by 5% * number of hostile candles.
Example: A level 1 priest is preaching in a province that has -4 dominion (that is, an enemy has 4 dominion there). His chance of successfully increasing his dominion (and thus reducing the enemy dominion from -4 to -3) is 10%. If he were preaching in a province with neutral or friendly dominion, he would have a 30% chance of increasing dominion. If there were a friendly temple in the province, his chance would be 15% (in the -4 dominion) and 45% (in neutral or friendly dominion).
Inquisitors preaching get bonuses when within hostile dominion. Their priest level will count as double for purposes of preaching under these circumstances. Effectively 60% * priest level - 5% * enemy dominion level.
If the dominion in a province is as high or higher than 2x the priest level (including the temple bonus of half a level) then preaching will have no further effect in this province.
Preaching-related dominion spread happens before combat. This can be very relevant in besieged forts where both sides can be preaching in the same province trying to control dominion.
Several nations are also able to spread dominion through blood sacrifices. To conduct a blood sacrifice, a priest of the appropriate nation can sacrifice a number of blood slaves up to and including his priest level. The province he occupies must contain a temple. For each blood slave thus sacrificed, one temple check (described below) is generated. Thus, blood sacrifices can be a powerful method of spreading dominion.
Apart from the above methods:
Provinces within a nation's dominion will have their scales shift towards that dominion's scales configuration. More candles means the scales will be more drastically affected.
If a player's province has their enemy's dominion in it, the province will not benefit from the enemy's order, production, luck or magic scales. The enemy's turmoil, sloth, misfortune and drain scales will still have an effect on the province, however.
EA Arcoscephale, MA Arcoscephale and LA Arcoscephale
Arcoscephale will scry on all provinces under its dominion. The information gained from this will be available to disciple players as well and is more accurate than normal scouting reports.
Mictlan (EA Mictlan and LA Mictlan)
In Early Age and Late Age Mictlan has dying dominion. Mictlan's home province, prophet, and temples do not spread dominion. Its pretender checks are half as effective as a normal pretender. The only way for Mictlan to spread dominion (aside from the pretender) is to conduct blood sacrifices.
The dominion of this nation follows some special rules. Oni are wild, ugly, and mischievous demons that thrive when the land is in turmoil. Oni will appear in all temples that are inside Yomi’s dominion. A high Turmoil scale will increase the number of Oni that appear in the temples. The strength of the Yomi dominion itself does not affect this, as long as it is at least 1. The location of the temple determines what type of Oni might appear – mountains or highlands are required to get the most powerful types. Cold or Warm provinces often result in the Ao-oni or Aka-oni that thrive in that type of climate. Temples in temperate provinces without mountains or highlands will only get the least powerful Oni. Oni generals also attract Oni if they are in a province with Turmoil scales or Unrest. These Oni are only of the least powerful type. Yomi’s dominion is not required for this.
Disciples to Yomi do not get this dominion feature.
Spreads insanity to all non-void beings and madmen will emerge to help in the war. Both effects will also happen in lands owned by disciple players and the disciple players will be slightly protected from madness just like humans in R'lyeh. This protection is far from adequate however and being a disciple to a R'lyeh god will not be easy.
The dead will rise to server Ermor and the living will die so they can rise later on. These effects will also take place for disciple players and the undead will obey the disciples when they appear there. The disciple players start with full population in their realm, but it will die quickly and undead will rise instead. Being a disciple of Ermor will not be easy. Ermor’s dominion also sense any unburied corpses in the provinces it covers.
The living will die and be animated by vines and roots to serve in the war against the world. Manikins will rise from the corpses of humans, animals, satyrs, harpies, minotaurs, and other creatures animated by the vines and the malign will of the God of the Vengeful Woods. Disciples will also get this effect and their population will soon be killed. Being a disciple to Asphodel will not be easy.
The dominion of C'tis will cause heavy rain that lasts for months at a time and turn the land into soggy wetlands. Mosquitoes will thrive and so will diseases. All warm-blooded beings without the swamp survival special ability will be affected by diseases and all enemy provinces under this dominion will have their income severely reduced. Provinces owned by C'tis will have their income slightly increased instead. Disciples are affected in the same way as enemies, but their sacred troops are immune. Underwater provinces are not affected, so it would be possible to have a underwater disciple without facing a ruined economy and a dying army.
Constructs will have increased hit points in this dominion. It will help disciple players as well as enemies should they have any constructs.
EA Caelum, MA Caelum, Niefelheim, Jotunheim and Vaettiheim
Spreads cold just outside of its dominion, too. It will have a 10% chance of changing the cold scale colder for each scale level it is currently away from maximum cold. Maximum cold is 1 for EA Caelum, Jotunheim and Vaettiheim, 2 for MA Caelum, and 3 for Niefelheim. The maximum cold is limited by the cold level chosen for that nation in pretender creation. Works just like usual when this nation is God.
EA Abysia and MA Abysia
Spreads heat just outside of its dominion too. Works just like usual when this nation is God. It will have a 10% chance of changing the heat scale hotter for each scale level it is currently away from maximum heat. Maximum heat is 3 for EA Abysia and 2 for MA Abysia.
Marverni, Sauromatia, EA Pangaea, EA, MA & LA Caelum, EA, MA & LA Abysia, EA & MA Vanheim, Helheim, Hinnom, Berytos, EA, MA & LA Xibalba, LA Marignon, Midgard and Gath
May blood sacrifice to increase dominion. This ability is not transferred to disciple nations. Disciple nations with this ability can still use it. These nations do not have dying dominion. Note that Marverni does not have any blood mages, so it will have very hard time finding blood slaves.
All Phaeacia’s commanders can sail (see Sailing ability, p. 59) if both the origin and destination provinces are in friendly dominion. The Dark Vessels ability cannot be transferred to other nations. Disciples do not benefit from the Dark Vessels. If Phaeacia is ruled by a disciple, it can still use its Dark Vessels in all lands under their pretender’s dominion.
Population will die off slowly but surely under the dominion of Therodoros. Friendly forts under this dominion will generate ghosts that will help the Pretender God. In disciple game this will also affect the disciples.
The dominion of Mekone is extra efficient at suppressing other faiths. When trying to remove the enemy dominion, the maximum strength of Mekone is counted as one higher than it really is.
MA Phlegra and LA Phlegra
All provinces under the dominion of Phlegra will have their unrest increased every turn. Higher dominion strength in the province yields a greater increase in unrest. In a disciple game this will only have an effect if Phlegra is the Pretender God and then it will affect the disciples as well. Being a disciple of Phlegra will be difficult.