We still lacks militaristic, pacifist, egalitarians, autotitarians... and hive minds. There were some neat concepts of how they should work proposed.
I proposed some ideas in my first Idea thread =D I'll repost them here.
Unknowable Builders:
-Their ethos is unknown and unknown both fanatic with ? marks.
-They build random structures in random areas and then leave, and the structures can hurt or help people but seem focused on the builders strange agenda.
-Sometimes they will randomly attack people and take a single colony but then later unexplainably disappear and return the colony to you.
-You can't communicate with them, they seem to communicate a different way every time and it doesn't make sense.
-Their appearance slightly changes (clothes, coloration, etc) over time as well in various ways.
and as for the explanation behind all this...
They are fanatic materialist and spiritual believing they could have ascended using technological means but they accidentally made their race partially sensitive and vulnerable to time, when you interact with them they think they are still at various points in time during their rise to power (for example the random attack and the relinquishing of the colony and the odd changes in communication strategy and behavior). The still sane ones are trying to build focusing structures to "recenter" themselves in time, you can decide the fate of this fallen empire by surreptitiously altering the structures, outright destroying them or helping them finish the network for different rewards and outcomes for the galaxy.
Other ideas for what the reasons could be can be added too to make it random.
Energy Harvesters:
-Desire star energy feeding off it to sustain themselves and will over time destroy the galaxy.
-Can attempt to destroy them or somehow find a way to sate their hunger or lure them into some sort of stasis trap.
-Can bribe them away with energy credits.
-Does not have territory but migrates onboard a titan.
-Do not have ethos
Pleasure Pontiffs:
-No longer have to work due to automation or enslavement fulfilling societal demands.
-Arrogantly believe themselves the pinnacle of all life and will enslave, torture or genetically alter other races for entertainment.
-Completely Decadent and selfish.
-Caste system created a depressed lower caste that is abused by the "nobles."
-You can inspire this lower slave caste to revolt and help them reform their empire.
-They will enslave and genetically alter races to be more pleasing or useful.
-Can sometimes dissuade them from focusing on you by giving them interesting information on other races.
Hidden Illuminati:
-Believe the galaxy will be destroyed by some grave threat down the line because of prophecy or observation of other galaxies. (can be spiritual or materialist but always also militarist)
-Desire to manipulate "worthy" races into becoming defenders of the galaxy and prepare the galaxy for their "guidance."
-They are hidden in some un-noteworthy star system with cloaked fleets and bases.
-Will violently destroy anyone who stumbles on them but will enigmatically benefit or push certain races toward hegemonic imperialism.
-Said races will believe themselves "chosen" and attack nearby nations until humiliated by a more powerful empire.
-The Illuminati will then focus their attention on the more powerful empire and the cycle will repeat.
-Each "chosen" race will be give clues about the Illuminati one can use after they are willing to talk about it from being humiliated to isolate where the Illuminati is.
-Or you can see what happens when the galactic crisis occurs ;D
