For my part, I want to tweak ethics divergence and factions such that early colonies, especially outside your home system, are prone to rebel and become independent before you have FTL. Letting them go and federating with them or forcing them to surrender / vassalize / become tributaries would drive you pacifist & egalitarian or militarist and authoritarian or some mix thereof.

maybe something like in independece day. An Alienfleet attacks u in a Pre FTL stage. You beat them and have maybe 50-100 years to prepare for there next attack. the attack should come in a Post Ftl stage and not to hard. Ideal to become a fanatic Purifier or at least xenophobe.
For the syncretic Evolution? watch the new movies "planet of the Apes"

@Richy- good idea for syncretic. Given an alien invasion is quite possible without additional events, I'm going to leave that one out.

Any ideas re: mechanist?

Oooh. Wonder if we can check for hostile first contact policy in neighboring empires and "suggest" that a that empire send a small scout force to your home system? If they're still STL, spawn an STL scout corvette or 2 of theirs in your home system so the war starts and the race for FTL is on.

@Pode- this I like more because it makes use of said other empires, that said, this would be a much more complicated event than the others because it involves more empires, so something for the future, agreed. (maybe a fanatical purifier 'crisis'?)

Oh yeah, we should always go after the low hanging fruit first.

I have several Ideas.

First is the already suggested Xeno Invasion. I outright suggest that the invasion could be either you being invaded or YOU invading them. This will be a several post musing because it is easier on me to do organize it that way. Part one is what I think is likely to influence if one is the attacker or defender and why.

I suggest making it something more similar to the Race invading: A nearby civ launches a invasion.

Now, it is safe to say Pacifists Civs will not likely launch a invasion..through they might lauch a "peacekeeping mission" to stop what they feel is a potentially warmongering neighbor. This should be more likely if the attacker is xenophile or Egalitarian and the defender is authoritarian or xenophobic. Militarists can be attacked sometimes by Pacifists, but more often than not will be attacked by the Militarists first. Xenophobe(fanatic or not) with non-fanatic pacifist should be very unlikey to do this, but should have a chance. As well,

Why would the Pacifists launch these operations in these cases? Well, it is possible that the public discourse went to "In order to have the Peace we want, we must stop them before they attack someone".

Fanatic Pacifists can safely be determined to never do this except in one situation: The person they are attacking is Fanatic Purifiers.

BUT: they will take a hit to government ethos attraction (this will handled by giving a penality to pacifist and a bonus to militarist) and happiness in any situtation they have invaded a nearby civ. After all, aren't we supposed to be spreading peace and love, not spreading war to another world.

This is actually why I suggest it should be possible to be the invader. It is entirely possible that in the process of this attack...your people change. Maybe become less trusting of xenos. Maybe they lose their pacifism for a more balanced stance.

Or Worse(better in some eyes): Become Militarist themselves. Stare into the Abyss, and it might stare back. And you become the very monster you tried to stop.

Having a third ethos of any kind is not really going to change things.

-FORMAT BREAK_


Militarists are to always be considered, Fanatic or not. This merely determines the likelyhood they are the attackers. As said, sometimes can be attacked by Pacifists, but moore likely to attack by far.

Xenopbobic/FanMilt and FanXenopbobe/Mil should be equally likely to launch. And by Launch, I mean as soon as they possible can. The first because Glorious war against the xenos. The second because conquer the xeno before they can pollute us.


Naturally, many people are not going to complain about such actions. After all, war is good, right? But it is also hell. If the war goes well, you now got a new planet! If not...people might turn their back on glorious war, the cowards. The longer the war lasts, the more people go pacifist. Maybe a more balanced approach dominates policy. Maybe You completely switch and everyone complains about your consitutional article forbiddening you from intervening in any wars despite the [Insert name here] MENANCE.

Of 3 way combinations, not likely to effect things much as xeonphobe.


--Format Break--

Xenophobe

Well, While XenP/Mil and XenP/Pac have been mentioned, this is not all cominations. There is also XenP/Egal, XenP/Spirit XenP/Auth. Being Xenophobic means they are likely to try if not Pacifist.

If they lose, Well...It should be random if they lose xenophobe or become even more so. That is the thing about xenophobia..

3 ethos designs are not likely to effect as much as the mil and fan mil does.
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Authoritarian basically might justify their actions as enforcing order on their neighbor. Losing should only effect the government ethos IF it goes so badly it causes a revolution. This mini-crisis should primarily effect the Xeno-Axis and Mil/Pac axis, not the Auth/Egal or Spi/Mat.

However, it is more likely than Egal to attack in my mind, due to the enforcing order part.

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Egalitarians should be most likely to attack in case of being democratic crusaders. Honestly, their reasons to attack are going to be mostly decided by the Mil/Pac and Xeno axis. It should only be changed from being a government ethos if it causes such a collapse in trust in the government that it causes it to be couped or a charismatic leader to basically make a authoritarian state. But that is more a different sort of crisis.

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Spi/Mat

Ok, while the primary decider on if these 2 attack, there is a catch: Materalists care about efficiency. However, the other ethos basically tell you what they think is efficiency. So it should have almost no effect on the chance. But Spiritalists? Depending on the ethos paired with it, it should have a major effect. If Xenophobe or Militarist it should be a major influence. Religion can be one hell of a drug. Same thing with Pacifism, but towards the other way. Most religions preach against war after all. A Spiritalist empire is going to take such parts of their religion seriously.

So while mats aren't hit by a lose unless revolution, Spi might be actually hit and your government move away. However, they might also go even more towards Spi, because their defeat must clearly been ordained by the Divine as a test of their faith!

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Hive Mind
Roll a dice. Either the Hive Mind decides it is worth the effort to expand to that world, or it doesn't. The Devouring Swarm Hive Minds should be more likely, but not an always will go for it.

Lose? Still Hive Mind.
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By now, you may have noticed I have not mentioned a particular situation for attacker:

Fanatic Purifer.

They can be Spi/Fan Xeno or Mil/Fan Xeno. Next patch at least. Either way, they should attack often. In case of defeat, the chances of them suffering ethos slip is slim. Because they likely already purged undesirables on their own homeworld. Only Revolution should be able to overthrow these guys by this point. And it should take a decent chunk of their people with them. And wreck half the tiles with blockers. And a chance of becoming a tomb world in a revolution. As I doubt they would willingly give up this power without trying to purge the weaklings who dare join the xenos.

PART 2: Nazi Olymics, The Long Snooze, and Boom Time and what happans afterwords.

First things first: Why am I bringing up Nazi Olymics? Well: The first broadcast humanity made to breach space in a coherent package was the 1936 Berlin Olyimics, where Hitler tried to show off Aryan prowess. Only for a Black Man to take Gold. It has been 81 years since then. Therfor, it is theoterically possible a civilization in that radius was graced by Mein Furher's embarsement.

I bring this up because sending a large army of millions of troops in random directions is how you start revolutions as people it pissed at your wasting resources. You want to launch an invasion towards a world you know someone is there to be conquered. Radio is pretty much the most reliable. So lets give everything within about 150 distance of the target defender a chance to launch an invasion. 150 distance because we need to be reasonable. We shall ignore the question of the actual size of stellaris galaxies. Let's have several events to begin this discovery period.


Somehow you pick up on radio transmissions from the Planet Bel-Air. You give the order to launch the invasion. So...one problem: How you gonna get there? You going to teleport. You have these puny little chemical rockets that will get there a long time from now. And you will need millions of troops. The enemy is going to have all the advantages on the defense. Like a actual production line to supply it's troops. You must bring a massive stockpile of ammo with you. And other supplies. So you need entire ships for that. You are going to need a lot of nukes as well. You need those EMPs.

You need to also have a freaking clue where you want to land your troops. So you need to send ships ahead. And the smaller, the better. Because your big transports are going to be seen lighting up their engines from beyond the Kuiper Belt...by our current tech IRL. Worse, it takes modern computers only a few hours to run the programs needed to search the skies for objects that stand out.

By stand out, we mean they might notice you because your radio leaked signals of about 20 watts their direction. 20 watts is as strong as your refrigerator light bulb. Well, ok, it might be weaker or stronger. But it is weak. A object 18 billion kilometers away with a radio signal of 20 watts(Also known as Voyager 1 in 2013) is going to be so easily picked out the main debate is not if it is alien in origin, but what to do about them.

Assume your enemy will know you are coming. Therefor, you must plan for this. It is going to be expensive. The invasion might end up failling before even getting started. The budget might just not exist for it. So you need to have several events for setting up the invasion. This WILL come at the cost of resources you could spend developing your home system. BE warned.

You will need to choose how your troops are prepared. Are they generational ships? Or are they cryo-ships? How many millions. How many supplies? How many nuclear weapons? How far ahead do you send the scouts? Do you send scouts? Will your ships do anything while in route? Do you send colonists after the invasion fleet?

Now this is done, you wait. Now, the thing is these ships are going through deep space. This something few of your ships have ever done. They are seeing this from angles you never have. So this is not a eventless peroid. You can potentially get random events that give research points. Physics is generated by events monitoring the stars and from events related to cryo-ships. Society is mostly from Generation Ships as well as larger forces(as military thoery is a society catagory). However, the tiny crews keeping things in order can generate Society. Engineering from just being ships sent out so far without any chance of support. It is a engineering challege on it's own.

You in fact should get major progress towards anything to do with spaceports, space construction, colony ships, outright get assault armies via event, and potentially based off of your choices even progress on AI or military theory techs. Since by even attempting this you have to make advancements in most of those to even have a chance of success.

So you crossed the great big yonder?

Well, If you scouted, you know what you are going to fight. Your enemy has been preparing. Or you got lucky and found the idiot corner. You need to determine how to strike. Do you invade the more well eveloped or less developed? One means a hard start but once done a easy finish. The other means easy opening...but the lack of industry means it takes a while to finish. Or maybe a mixture. The enemy will outnumber you, will be able to outproduce you, and has had time to prepare.

You however still have tens of millions ot troops. And the one deciding the landing sites is you. Not the enemy. The enemy is having to defend a entire planet. You can just focus on one area, and take out one of the strongest forces before they can bring their numbers to bare. Even if they have better troops this fact is still important, because it is hard dealing with such a concentration of troops. Espeically since nukes will be filling to EMP everything if possible.

MULTI-PLANETS
Basically, repeat on the other words until one side wins or a treaty is signed.

AFTER

If successful, have fun controlling a world(or worlds) of hostile aliens. A colonist follow up might help by providing loyalists. Fanatic Purifers have it worst however. They also are trying to kill these xenos. They really need that loyalists to show up.

But the enemy might fight on in the hills. Now, there is no way in hell they will suceed once you have gotten this far. Not by outright winning the fight, that is. They might however get so annoying you might just make them a tributary or vassal empire instead. Or even just abandon the planet. Unless you successfuly purge them

If you lose, wel, that is a lot of resources down the drain. Somone is going to need to answer some questions. And that is if such questions weren't already being asked. Both will change.

The defender is going to be prone to being more Militarist and Xenophobe over it for sure, the attacker already covered last part.


Now...what if one is playing with Colonisable Home System? You might not take all their worlds. Some worlds are taken, others are not. Perhaps you make a peace here.
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Counter-Invasion. Once one side invades, one might try to repay their enemy if they manage to not be totally defeated. In this situation, one just runs through the events again..unless one has gotten FTL in the mean time. And well, if a CHS split system is ongoing..perhaps the war might reignite.

@Malevolence Mechanist: After a World war the robots were build by the survivers to rebuild the citys. That could explain there small population

Dunno if this is necro posting, but i had this idea, and wanted to share it.
I am not sure if this can be made with stellaris mechanics, but it would be really cool to have another race spawning in the same system you spawn.

So you not only have to fight the "hostile nations" on your hw, but also another xeno races which would regularly send armies to seize your world. To make it more intense, it would be nice to give ships some really slow early game engines (same to hyperdrives, just make in-system movement reduced by 99%).

Or making events of nuclear strikes between you and that xeno empire (similar to the existing event of a meteor hitting primitives/ yoour coloniers)