Slavery boosts a population unit's usefulness for the empire at the cost of its energy and research production, as well as the Happiness of the pop. Patch 1.5 adds numerous enslavement levels and slavery type through the species rights system
Enslavement and emancipation
With the Slavery policy active, an empire can choose which species can be enslaved as well as how they are enslaved via species rights. Enslavement is done automatically based on the species and (in some types) what they are working on.
There are the following Enslavement options:
- No Slavery: There are a number of settings with this effect, but varying participation rights. All pops of this species are free. This is the default for every species that cannot be enslaved.
- Caste System: All pops producing "exclusively minerals and/or food" are enslaved. That basically applies to farms and mines. Several buildings that also produce Unity are not included, due to the Unity penalties. This type is only available for Authoritarian Authoritarian empires. This setting will maximise Chattel Slavery output, without causing excessive Unrest or additional Research and Energy penalties. It is the default setting for Authoritarian empires.
- Full Slavery: Every pop of this species is enslaved, regardless of what it produces. This is a requirement for a certain set of slavery types. It is only available for Xenophobe empires and cannot be applied to the empire's founding species.
Slavery types are as follows:
- Chattel Slavery is forced menial labour. Unskilled production (Food and Energy) is boosted, but there is a penalty to anything more skilled, especially science.
- Domestic Servitude represents both plantation labour and indentured servitude. Domestic servants do not give a boost to Mineral and Food production, and have a small penalty to the production of other resources. Their benefit is a Happiness boost to all non-slave pops on the same planet. Another benefit is that they suffer less Happiness penalty for this kind of slavery, reducing Unrest from them as well.
The next two are only for those with the Utopia Expansion:
- Battle Thralls have no boost to Food or Minerals production and a moderate penalty to all other production. Armies built from the pop are much stronger, however. Full Slavery required.
- Livestock produce a fixed amount of Food per month. This is the "sustainable" variant of Food Processing. Full Slavery required. Does not affect Robot pops.
- Iron Fist governor trait increases slave productivity by +10%
- Slave Processing Facility building increases productivity by +10%
- Slaver Guilds Civic increases slave productivity by +10%
- Share the Burden edict increases productivity by +10%
- Stimulant Diet is a repeatable technology, which adds +5% to both Minerals and Food production of slaves
- Slavery and slavery type are set for the entire species across the empire. It is less flexible than the Caste System available to Authoritarian empires which enslaves on a per-pop basis.
- All types of slavery will heavily penalise science research and Unity generation, and species being enslaved should not use either of those building types for best efficiency.
- Chattel Slavery works best with slaves in Mines or Farms but is nearly useless for science, and the least effective for energy credit production.
- Domestic Servitude provides a happiness bonus (and helps reduce unrest) but is less useful for production than the other slavery types.
- Battle Thralls are obviously the best option for creating armies, but it also has the least penalty for generating energy credits, while leaving mineral production at the default level.
- Livestock are completely useless except to generate 3 food per pop per month. Do not waste minerals building on a livestock pop tile. Livestock slavery is best used as a stop-gap in the early game to boost food stockpile to maximum without costing energy to run farms, but should be phased out for regular farms if you require more food later.
- Setting a slave race to Limited Military Service will allow building of armies with that species.
- Any planet with slaves should have a full complement of defensive armies to ensure that unrest is contained.
- The direct bonus is the increased production from the pops themselves or from free pops on the same planet.
- It also boosts Authoritarian or Xenophobe Ethics Attraction for free pops on the same planet.
- Slaves cannot join Factions and use the baseline Happiness of 50% regardless of Ethics (see below).
- Slaves operate on a Impoverished Conditions Living Standard. Under Caste System this will override the Living Standards selected for the species as a whole.
- As a combination of increased income and poor living standards, slaver empires tend to have a lot more Minerals available - unless they go for Domestic Servitude.
- Using Caste System, a player can move pops with ethics they wish to suppress to tiles where they become slaves, thus preventing them from strengthening an unhappy faction. The slave unrest does then have to be counteracted though. So this isn't a perfect fix.
- Slaves are unhappy. -20% for Chattel Slavery and -10% for Domestic Servitude. This is in addition to the penalty from their Living Standards.
- As a result of poor Happiness, slaves will produce considerable Unrest. Considerable Armies and other Unrest suppression will be needed to counteract this.
- Slaves are drawn towards Egalitarian ethics. As they cannot join factions, this ties more into the Dangers section below.
- Slaves increase Unity cost for Traditions.
- As slaves cannot join Factions, a large number of pops will not be eligible for forming of factions. This will delay the forming of happy factions and the associated Influence income considerably.
- Extremely Egalitarian empires will have issues with the use of slavery.
- A Unrest-incited slave rebellion is always a danger. The rebel slave empire will try to join a Egalitarian empire after conquest of the planet.
- The "Stop Atrocity" wargoal has two effects: First it will cripple the Mineral (and possibly Food) income of the empire. Secondly all the former slaves will emancipate as Xenophobes or Egalitarians and are extremely likely join factions almost instantly. This could actually result in even worse Unrest then the slaves themselves.