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human
[Warhammer 40k] What can I expect when the Imperium show up?

I live on a world that is culturally & technologically identical to High Terra circa 2016. We've only just found out about the rest of the galaxy. (Warpstorms or something I'm no expert.)

What can I expect to happen if the Imperium of Man shows up? Genocide? Slavery? 

Clearly they're the lesser evil compared to most but would we be better off with the Tau? Maybe we should go with this Slaneesh person who seems like a fun dude/tte?

Thank you in advance for your advice.
gpt
**Imperial Diplomat** will arrive and they will make demands, demand of complete and utter loyalty to the Imperium. They will have charts to show off the status of worlds that said "no" to this deal. Also images of burning worlds.

If your goverment does not accept, a invasion force will be sent round whenever the Imperium get around to it. Give it 150-200 years.  
You will of course get your arse handed to you and your world will now have a black stain for pendence.

After (continue here if government accepted offer), Imperial missionaries will arrive from the **Missionarius Galaxia**, the fact that none have heard of the Glory of the God Emperor means they have a lot of work ahead of them. The **Ecclesiarchy** will probably set up a **Schola Progenium** as well for orphans. **Creed Temporal** will visit and give you a massive bill on construction of a few new churches, don't worry, be faithful and you will be rewarded (with brand new churches).

The **Administratum** will get busy, a full overhaul of your worlds production and then a tithe will be set. Any objection to this tithe will be meet with judgment of a traitor. Ignored if you are lucky. Of course, this tithe will probably be a bit more then what your world currently can produce, so expect a lot more factories to be build to support it, and a lot more hired factory workers. All installations the administratum demands will also be set up, buildings for adepts to work,  **Adeptus Arbites** will get their own station, the **Planetary Governor** will be elected if the world does not produce one themselves.

**Adeptus Astra Telepathica** will send some low ranked psykers to start looking over the amount of psykers you got and take in those you have. The Black ship awaits! A communication array will also be constructed, you got to have the ability to message the Imperium when shit goes down and someone is threatening your tithe after all.

Any local army will be remodeled to fit the **PDF** system, this local army will also be used for **Imperial Guard recruitment** if that is part of your tithe.

And finally, the **Adeptus Mechanicus** will come around to look over your technology, heretek is very bad you know, you don't have any heretek do you? If they find your world worthy, you might get a **Manufactorum** to improve your tithe. They will create a base for themselves however and they expect all technological companies to go thru them now. To refuse is not good for your health.