The Vudu Kult is a four way synergy between the budding trait, subterranean origin, the death cult civic and permanent employment civic for vast zombies hordes clawing their way out of the ground!
Besides regular organic reproduction the vudu kult raises additional pops as zombies through the Permanent Employment civic. These pops are made using the pop assembly mechanic which is also fed by the budding trait of this species.
Permanent Employment gives a flat value to pop assembly, while budding adds a bonus to pop assembly in proportion to the total population. Together, in synergy, they deliver an explosive and sustained population growth of zombies.
A quirk of this combination of permanent employment and the budding trait is that these zombies do not actually need a reassigner job to reproduce because budding also creates pop assembly.
This means if some of the Vudu zombies are acquired by an empire without permanent employment they will still reproduce. One implication of this is to screw with mechanist or materialist factions because robot assembly uses the same assembly window.
They will also begin assembly on new worlds which do not have a reassigner employed yet.
The death cult civic allows for pops to be sacrificed for empire wide bonuses. For the vudu cult pops are numerous and so these sacrifices are cheap. The best of the three sacrifice edicts for the Vudu Kult is the Bounty Sacrifice, which delivers bonuses to minerals and energy but also pop assembly. Every sacrifice here creates more zombies!
Moreover with the cave dweller trait, from subterranean, the zombies are actually not bad at working mines for minerals.
Unfortunately the zombies themselves can not be sacrificed so they will tend to accumulate. They can only be given worker tier jobs too.
Fortunately subterranean allows for uncapped mining districts. When the zombies come up from the ground they bring the treasures of the earth with them.
Spiritualist is required for the death cult civic. The unity bonuses and discounts on edicts are very useful here though.
The self-assembling zombies of the Vudu Kult will tend to be a very worker based economy. Authoritarian gives a bonus to worker output. This ethic also allows the zombies to be enslaved which opens up many interesting options, especially as happiness is not an issue for the zombies.
One type of slavery that might suit is domestic servitude. This way unemployed zombies will contribute amenities.
As an alternative to authoritarian ethics, pacifism, xenophile, xenophobic or militarist are lesser options.
Pacifism reduces empire size from pops. The vudu kult has plenty of them. The bonus to stability is okay too, although the zombies are unaffected by happiness.
Zombies actually make quite good clerks, besides miners. The job production penalty they have does not apply to the amenities and trade produced by clerks. Their productivity as clerks is further enhanced by their low upkeep.
So the Vudu Kult could potentially run a clerk heavy merchant build, using mercantilism tradition, alongside the mining. In that case Xenophile might be worth a look. The Vudu Kult is a mega-corp too so xenophile helps with getting commercial pacts for branch offices. Commercial buildings compete with sacrificial temples for building slots though.
Xenophobic with genetic engineering could allow the creation of a sub-class of edible zombies!
Budding is the main trait to have for turbo powering the organic pop assembly from permanent employment.
Death priests make society research and unity, as do mortal initiates, running heavy on them suggests giving them traditional and natural sociologist traits.
For the negatives, I suggest the decadent and wasteful traits. Decadent applies a penalty to worker and slave happiness. Before long worker jobs will be filled up by zombies who are unaffected by happiness. Mortal initiates will still be affected by this penalty but the impact will be small, especially when also running a stratified economy living standard.
Wasteful increases pop consumption of consumer goods but Vudu zombies have no consumption of these things. This penalty will only affect the minority of the population employed as specialists and rulers.
Artificial worlds like ecumenopolis, ring worlds and orbital habitats are not particularly great for the Vudu Kult. We want to be on more natural worlds to better leverage the subterranean trait and swarms of worker tier zombies.
The Vudu will quickly fill up planets though so the mastery of nature perk can be useful for adding a couple more districts. Also worldshaper is handy for making gaia worlds.
The Vudu are rich in society research so the engineered evolution ascension path is good pick. Genetic modification projects cost society research.
The Vudu are strong in unity, society research, pop growth and mineral production.
Zombies can only take worker jobs and they reproduce fast. Creating enough jobs to keep them gainfully employed can be challenging.
There we go, one of the most fun and weird faction builds I have ever created. Will you give it a try?