My current favorite is a lovely state called the Domination
Human main race- slow breeders, unruly, thrifty, intelligent, quick learners (Dominus)
Necrophage origin
'Klingon' serf/aspirant race -slow learners, fleeting, rapid breeders, strong (Servus)
Imperial Fanatic Xenophobe/Militarist
Civics: Pleasure Seekers, Reanimators (third civic Memorialists)
Homeworld: Tartarus, Superhabitable (planetary diversity mod)
Ascension: Biological
I keep minor races that can inhabit biomes my core races don't favor, otherwise they get necropurged.
Goal: Galactic Emperor (or I go Crisis if the mood strikes)
I don't have a decent screenshot of them, but here's one from my last successful Imperial campaign
I based them on the Necromongers from the Riddick movies combined with the Gou'a'uld from StarGate. Mainly a fanfic crossover of the Draka/Stargate series. They are cruel, manipulative, ethereally beautiful and obsessed with carnal pleasures and material delights. And of course of accruing power and dominating all lesser species. Favored individuals from subject species are 'offered' Ascension, where their minds and bodies are molded to the perfection of the Dominus and take their place as citizens of the Domination. Un-needed species are violently turned into Reaper-style genetic goop for re-assembly as Dominae.
All must submit to the Domination in one way or the other.