The holy slavedrivers have their whole mechanics in the name already: They are religious and they are slavedrivers. Now slavedrivers is an amazing yet dangerous racial affinity that makes any population that isn't yours but lives on the same planet as one of yours produce 100% more FIDSI. It creates -10 Happiness per supressed population though.

That is where religion comes into play. The third unlocked law – Saints and Sinners bill – sets your global happiness to content or happy if you are a republic. That means you can expand as much as you like, have the most slaves as possible and people still like you.

Gameplay Affinity: Slavedrivers
Visual Affinity: Riftborn
Government: Republic
Home Planet: Atoll

Political Impact: Religious, any addition you like (Anti-Pacifist and Anti-Militarist help)
Bonuses: Loyal Citizens, Engaging Denizens, Boundless Collection

• Ace Senators
  
• Pilgrims minor faction population
  
• Smooth Talkers
  
• Strange But Good
  
• Guardians

You might ask yourself: why Riftborn visual affinity? This is a key aspect to the race because it helps manage your population much better. Remember you only need one of your own populations to make all the other factions' pops into slaves per planet. The Riftborn visual affinity forces you to construct your own pops instead of growing them with food. Like that, you can create a pop on each planet and let the rest fill up with slaves.

In a Republic you have less control over the politics than with a dictatorship, so much is true. However the Republic allows setting the approval to happy instead of content with Saints and Sinners bill and many improvements only work on happy or even ecstatic. And republics offer the possibility to have a strong influence on the elections. If you use Strong Arm Lobbying, you will always win the election with your favourite type of government. In addition you can use more laws and get less unhappiness from parties without senate representation.

In general you have many options. You can activate happiness boosting laws, settle on small planets so the unhappiness from slaves doesn't go overboard or you cull the herd. This last option is presumably the best. It takes one turn and increases happiness and food by 25 for 10 turns at the cost of a slave. These bonuses stack up and once you've got a decent food production or culled the herd a couple of times, you will get the dead pop back within 1-2 turns. So almost nothing lost, much gained.

When you colonize a new system you will always have a pop of your own faction there. That means for getting slaves there you need the first spaceport a.k.a. the first system level improvement. You get it by researching 2 tier II techs in the economy and trade tree. Then you can select 1-3 minor faction pops from your home planet and ship them off to the colony. Not only does that give the new colony a good boost, it will also enable your empire to grow faster as a whole.

After an invasion you may find that the taken over system is too full to construct own population to make the residing ones to slaves. Immediately setting the approval to happy with Saints and Sinners bill also doesn't drastically decrease food production as you might be used to from invasions, thus there won't be any people that die. Luckily, faith is the answer – yet again. The law Species Stability prevents any population apart from your own to grow. So if you need to grow your population on a full system you can either cull the herd a couple of times or send some pops to systems with some capacity left. Then in the following turns construct your population. Once you are done, make sure to deactivate the Species Stability law again because it will globally bring your empire to a halt in growth.

While the early game is not very easy or just takes a lot of micro management due to managing happiness, once Saints and Sinners is activated you can turn towards any goal you like to achieve. I went for expansion victory because I already started with a big territory and due to the massive Science production from my slaves I out-teched the enemy with my fleets. In wars I just started invading the AI's planets until they started begging for mercy. I signed truce treaties by demanding several systems. In 3 very short wars I doubled my system count. And the best is, they are immediately happy due to Saints and Sinners bill.

Fanatics have always been powerful throughout history, no matter in what field fanaticism was practiced. It is not so much different in Endless Space 2. This build is very strong from the beginning and gets out of control in mid and late game. Your expansion is only limited by your early happiness and planetary colonisation tech. I have yet to find out if it is more powerful than an Ecologist Ship Bound Riftborn as this is the only other OP build I know of.

I am always looking forward to comments, improvements and thoughts.