Ancient Astronauts: Almost certainly happened in at least a few times and places, for the same the-Galaxy-is-old-and-relatively-life-rich reasons that are why half the systems in it are practically knee-deep in elder-race trash. Also, technically, connected with the origins of the eldrae and greenlife in general from prehistoric Earth, although given
Lizard Folk/The Reptilians: About the closest you’ll find are either the kaeth (bipedal, vaguely draconic/saurian, and also from such a metal-rich world that their scale-analogs are actual metal) or the mirilasté (legged serpents). Both defy the traditional reptilian-appearing race stereotype by being civilized and urbane, although the
Amazon Brigade: For historical reasons having to do with the local units they used to be, the Empire has several Legions that meet this trope (and, for that matter, its diametric opposites (yes, opposites; not every species has two sexes)), although most legions are mixed. Of course, in-world, no-one finds
Living Starship: The genesplicing esseli and the residents of Kythera – the Empire’s masters of biotech – are the chief users of this sort of technology in the Imperial context, although they’re by no means the only ones in the Associated Worlds to go for this sort of thing. Although,
Flesh Versus Steel: Both have their partisans within the Eldraeverse – many branches of the Silicate Tree are steel fundamentalists, although how much of that is rationalized hatred of their organic creator-enslavers is open to question, and they’re not the only ones. Likewise, there are partisans of the purity of
Living Relic: Quite a few, including some cryonauts and other last-survivor types, but the most common form of these is still-readable archives left behind by dead civilizations. Many of which archives include suspended mind-states – sometimes biological but more often AI – or recipes to create AIs, as part of their contents.
Alternative Calendar: Several. There’s the regular Harmonious Calendar, which is based on Eliera’s – as the homeworld and the throneworld – cycles, but also serves as the de jure calendar for the purposes of the financial year, official record-keeping, and suchlike. In turn, it’s based on weavetime, which is
Sealed Evil in a Can: Probably more than a few of them, buried in ancient ruins and archives. A few are physical artifacts, but most are information – recipes either for software or for assemblers. And rather inconveniently, they’re mixed in with not-much-really in a can, incomprehension in a can,
Gone Horribly Right: An unfortunately large number of experiments with recursively self-improving seed AI are probably the most significant examples, here, for which see that half of the entry under AI Is A Crapshoot. And for the consequences – well, there are quite the wide variety there, but for a good
Living Forever Is Awesome: This is, essentially, the default position of the immortalists, which include all of the natural immortals. There are so many places to go, people to see, things to learn, things to do, it’s impossible to become truly bored… and, oh, yes, do see also Eternal
(Here, have a vaguely Christmas drabble.) On ancient Eliera, they roast meat in the snow and light fires for the return of the second sun. At the peak of Kythera’s deep winter, they dine in the Deep Vaults while robots above set the atmosphere on fire. In drift-habitats across
All Planets Are Earthlike: So very averted. Actually, I think somewhat-terraformed Mars-like worlds are in a slight statistical majority among the Empire’s inhabited planets, but there’s plenty of other non-gas-giant like inhabited worlds as well, and that’s certainly not counting all the non-technically-inhabited ones. (And even the