A mass of stars, a remarkable one hundred six light-years in radius, shines just barely outside of the galactic disk. From its vantage point the galaxy is a plane of stars, stretching seemingly forever in all directions, with the spiral pattern quite difficult to discern. Within the cluster- some say a bound starway, but most settle on "stellar sphere"- lie approximately seven million stars, primarily older and averaging yellow-orange in hue (adjusted for how much light such hotter stars put out), with more giant stars and less hot stars than are to be found in the disk. The predominant "theme" of the region, if such a thing can be divined, is that it is ancient- but whether this is the truth of the region or if it is by some design is uncertain. Either way, an in-depth look at its stars reveals a startlingly variable metallicity- and considerably more verdigris fusors (or blue dwarfs) than is expected for any time period in the next hundred billion years.
Further, it has a long history of habitation- the few scholars of the Ecumene that have reached this place note that while its situation does not conform to the "bloom" archetype of the wider galaxy (instead of a single spreading burst traversing the whole galaxy, lasting thousands of years in a region and taking some million (or three) years to travel the galaxy; there instead appear here to be tiny "wildfires" of sudden starfaring that quickly settle down and stay in one place (physically and not) for extremely long periods of time) it can still definitively be seen to include works from before what in the Ecumene is known to be the first bloom. This means that every star in the stellar sphere, if explored thoroughly enough, has if not living civilization- at least one, more commonly thousands and thousands of pieces of evidence pointing to its prior presence.
What follows are several writings, musings, and notes on the Ecumene's sister setting and the stellar sphere it inhabits.
So in the Ecumene, wormholes and gates vary greatly- from ragged unstable wormholes like whirlpools in the sky to tortured torn-open paths into arcane dimensions to simple lighthouse gates which enhance other FTL drives. They vary from tiny comms-only portals to the megametre-wide emissary from the Chloric Vault. Some are nearly instant (but consequently barely long-range enough to cross the distance between worlds) and some are even sublight. Many are of limited gauge, with larger craft incapable of passage. Craft passing through may appear complete until passing entirely through and disappearing, or they may seem to slide out of existence. One thing, though, is shared by nearly every last one of them: they are flat and circular in two dimensions, the rest of their higher-dimensional geometry hidden from view.
This is not so in the Stellar Sphere. There, nearly every wormhole and gate retains a curvature in the third dimension- a spherical shell over transdimensional workings. They vary just as much as their Ecumenical counterparts- even more, truly. In the Stellar Sphere wormholes can be cousins of black holes, there are wormholes and gates as large as stars, and while driving a train through a gate is inefficient there are gates which have multiple destinations depending on where a travelling object enters the sphere. There are two other main quirks of these entities in the Stellar Sphere- many wormholes and gates are fully affected by gravitational forces and do not only orbit parent bodies, but sometimes even host orbiting bodies.
In the Tskenathis Coil region, one relic megastructure outshines nearly all others known. Within a wide net of gravity-manipulating stations and the small nebula they keep stable lies the crowning achievement of the Rassath Grey Crescent technocomplex: a vast star-encircling structure in the shape of a disc. This structure outstretches the size of any comparable one- its central star is kept stable and at a luminosity befitting a bluer mint-color star (despite the star's relative redness) through techniques themselves beyond many similar structures, and has been kept in roughly the same state for billions of years. Across its two habitable surfaces, each with a surface area comparable to billions of more standard habitable worlds, various likewise arcane technologies maintain not only varied atmospheres but also keep the ecosystem (if a patchwork composed of uncounted separate abiogeneses can indeed be labeled as an ecosystem) dynamic and constantly evolving. It is considered very likely that the disc was created as a sort of microcosm- possibly as a way to observe the evolution of life and civilization in an environment unconstrained by petty concerns such as global environmental change and the short lifespans of bright stars. The most stunning piece of evidence for this is the structure of the landforms of the disc itself- while tectonic processes are simulated in the star's-width subsurface of the disc, they are shepherded (presumably as insurance against continental drift on absurdly long timescales) into the rough but noticeable (at least, at magnifications high enough to percieve the disc's surface as anything but a slightly tinted blue mass) fractalized form of a spiral galaxy- with much smaller spirals helping fill the gaps between arms.
Upon the disc are countless evolutionary experiments, tweaking variables like atmospheric and surface composition many thousands of times over with the end result that what one might assume is a single somewhat-uniform biosphere varies on scales as small as just a few planetary surface areas. With a properly magnified view of the disc, this can be easily seen from the extremely varied colors of the land- some popular colors include green, purple, and red. Life-regions "bordering" each other may use different chemistries that can both be viable in similar environments, or have very similar chemistries but have concentrations of various materials toxic to each other- though as a general rule similar regions are kept near each other to allow for a degree of intermixing. Many of these experiments have given rise to sapient life- hiveminds, groupminds, and singlet minds are all present; both naturally-evolved and created by other sapient life. These civilizations follow similar paths to observed spacefaring ones- alternating phases of expanding, waning, migrating, and staying in roughly the same area for up to a dozen million years, with a few having been recorded to traverse notable amounts of the entire disc (though obviously not all at one time).
Their technological prowess varies- many are known to have technology matching that of life beyond the disc, though very few have technology suited for interplanetary traverse and some have acquired said technology from others. Countless attempts at "enlightening" the peoples of the disc have been made- both towards a certain ideology and towards certain technologies- but these are doomed to not affect much of the disc even at the most fervent pace. In any case, the systems maintaining the disc and its environs allow this activity- something they assuredly don't do for concerted attempts to probe the inner workings of the disc itself. In the nebula surrounding the disc, in addition to the metals siphoned out to keep the star alive and the vast reserves of hydrogen to be put in for the same purpose, there is a vast graveyard of such would-be plunderer ships- themselves host to people that make a living off of harvesting them.
A state regions in [sister setting], especially on the Rassath disc, can often fall into is that of a peaceable stagnation: any technological and political regime that, unlike what anyone with a concept of history will tell you, stays largely the same across extremely large timescales. These states are immensely varied, but the largest thing they share in common is that they are voluntary: individual-driven societies can be changed quickly even if splintering is required, and hivemind-driven ones can simply become bored or fragment. As a result, a state acceptable to all can be maintained for bizarrely long periods of time, spinning off societies that are less content to operate at the same level but which only rarely interfere with the content groups that birthed them. One byproduct of this is the creation of machinery that is manufactured in largely the same fashion for centuries- especially war machines, as the peaceable stagnation state is unlikely to produce an actual war but rather tense-yet-quiet standoffs between polities.
One long-lived example of this is the Untrilar Un.259.4SP Upkettle, a twin-engine turboprop biplane from the Second Council Republic of Curinet. Initially built as a prototype mixed-power carrier fighter, with one turboprop in the nose and one turbojet in the rear, this quickly proved unsatisfactory- as such the third prototype was reconstructed to feature two engines side-by-side in the nose driving contra-rotating propellers, briefly affording the Un.252 the title of the smallest triple-engine aircraft then in use. Unfortunately for the 252, it was still completely unusable as a fighter (though there are reports that it briefly broke the speed of sound). As such, the aircraft's turbojet was removed- and after a series of design changes the ungainly aircraft was repurposed as a patrol/attack/anti-submarine aircraft with a total of three seats. This produced the Upkettle that is still in service today, seventeen hundred years later.
Patrols of Upkettles have flown for approaching two thousand years, outlasting practically everything built alongside them- four hundred years in the Second Council Republic was replaced with a Third and quickly a Fourth, two hundred years after that the Untrilar Design Bureau attempted to escape collapse by selling the design, and three hundred years later the carrier designs of the era of the early Upkettles were deemed outmoded and replaced. By this time, however, the Upkettle was a design even crossed the Council Republics' stormy rivalry- most prominently by the satellite Republic of Turish, which adapted the aircraft to its own carriers. By two hundred years after their retirement in Curinet, Turishian Upkettles would become capable of operating on modern carriers. With the Upkettle still being a useful and competitive aircraft in the roles it was built for, they were quickly re-adopted in Curinet. In this way, the aircraft precipitated one of the largest changes seen yet in that stagnation: normalization of relations between Curinet and its bitter rival.
As such the Upkettle is now over six hundred years into the second era of its reign, and it seems likely the unique double-turboprop biplane will see service for centuries more- beating all comers. In the long time the Upkettle has been used, its design has been upgraded and changed many times- but even those building the Un.250 would recognize it as their aircraft. As a result, though, there are hundreds if not thousands of variations of the Upkettle not only proposed and built but in use today. These include relatively similar variants, designed for use in anti-electronic or delivery roles aboard carriers or as land attack planes, as well as wildly divergent niches- from trainers to tankers and reconaissance aircraft all the way to civilian agricultural planes, small airliners, and even firefighters. A swept-wing jet fighter version has even recently been flown, thought it seems unlikely to excel.
The Kozzavel Strip is a string of several dozen bright stars and their companions in a parcel of the 4th ring of the downsouthwest octant of the local stellar sphere. It is known largely for one thing: its eighty-plus stars are host to one of the largest coherencies in nearby space. The hivemind that controls the Kozzavel Strip is extremely old by many reckonings, and by its own measure is approaching fifty million years old. Archaeological methods are inclined to agree- if it has not usurped the constructs of a long string of similar previous civilizations, it is almost certainly that old. As with intelligences even a hundredth its age, Kozzavel is deeply idiosyncratic- a large part of its cohesion is speculated to come from the fact that it embarks on large megayear-long endeavours that are so large that any individual unit can perform any number of tiny specific tasks or interests within it and still be satisfied by the end. Its current endeavour seems to be "beautifying"- the orbital debris of millions of years straight of building, not to mention that of innumerable civilizations from before (some of the better-preserved ruins in the local stellar sphere) must be collected, catalogued, and put into the most aesthetic orbits and combinations.
Part of the reason for this is a now largely-completed project: the habitiformation and seeding of as many words as possible within the Kozzavel strip. This was done to extremely varying aims, but most importantly produced thousands of space stations and habitats for the delivery of resources and cultivation of the nascent life to be placed upon said worlds. Some of these will remain in orbit of their subject worlds, but most are to be moved to lagrange points and disparate orbits. This has also resulted in the largest exploratory endeavour Kozzavel has embarked on in recent memory- an attempt to acquire the most efficient drive unit that expels the least material, in order to preven the production of further space debris.
The Harp Fiefs are a collection of thirty-six lighthugger coherencies in the Damattu Drift region, each controlling a single highly populated world and a few dozen other words (usually across a few star systems) that provide for the planet. The governments of the fiefs vary, but each predicates its rule on control of one of the Harps: rudimentary ansibles that the Harp Fiefs have developed a complex system for properly operating. Each Fief maintains a corps of dedicated Harp operators, which in many Fiefs resembles a second set of ceremonial nobility. It is considered likely that the creation of a new FTL method in the region would not greatly destabilize the Fiefs- rather, so long as each of the equally-matched polities received similar access, the symbol of governance that each of the Harps have become would remain more important than their actual abilities.
The Myllodit Arc region plays host to one of the more complete ancient networks of artificial wormholes. Constructed by the local Blue Ring Luminaire culture (so named for the lamps ubiquitous in located dwellings) as they spread from their homeworld (now taken by proper motion beyond both the region and the local stellar sphere), each wormhole consists of a blue sphere glowing with imaginary radiation. "Beneath" the surface of the sphere lays an inside-out pocket of spacetime, which contains the machinery allowing the wormholes to function as more than a fancy bauble, and around the sphere itself there is a ring that, if correctly anchored, allows the wormhole to be moved. A properly encoded signal can be parsed by the machinery to transmit matter or energy to any other wormhole in the network.
There's just one catch: Nearly all of the large wormholes in the network have evaporated, leaving only the centimetres-wide communication wormholes (and the useless support armatures for the larger wormholes, and theoretically the pocket dimensions themselves may be intact... but they're theoretically irretrievable). No other FTL technologies are in wide usage in the Myllodit Arc, so it is common for large interstellar haulers on their months-long jaunts between nearby stars to carry their own communication wormholes with them rather than use other types of ansible.
There are prominent exceptions to every rule- some more prominent than others, to be sure, but all evident.
...but those exceptions tend to be governed by their own rules
the hivemind setting's ftl is more based around wormholes and simialr than the ecumene's- no less diverse, but more focused
a perennially-inhabited system might have dozens upon dozens of interstellar networks connected to it... but even the ones that can be activated tend to only be activatable for a given connection. easier to power up two gates than two million, and such. cuz that's the thing: everywhere has had people in it. they might have left in a hurry, but even so! there aren't places where you can confidently state that nobody has ever been here.
And those million stars are spiderwebbed with hundreds of separate interstellar travel systems. An odd mass in the far cloud of one star is discovered to be a wormhole that since it was created was kicked outsystem like a comet, in the trojan point of one planet is discovered a battered hypergate, networks old and new are used daily....
STL starships of all kinds are much more common in the globular cluster mostly-gate-like-rather-than-ship-like-travel prominent-hiveminds layers-on-layers-of-ancient-history sister setting to the ecumene, partly because they're efficient enough to do non-priority work in a world where stars are light-years apart at most rather than at least and partly because they're the only things that can definitely go everywhere (the myriad interstellar gate networks, new and old, all have their own restrictions; many FTL drives don't like globular clusters etc; maybe they just plain missed a buncha FTL drive types)
this means i can do scary shit- dip my toes into the star-spanning megastructure bullshit
and, because of the rules of the setting, i can ignore the other problems with that; i can build systems full of laser platforms propelling dwarf planet-sized lightsails between systems
definitely the good thing about the whole thing where stars in the globular cluster if they're connected by FTL it's gates and such: i can draw constellations! and they're REAL! maybe proximity of constellations is just governed by if there are stars near each other by other methods...? holy shit its a mix of a transit system and a constellation
for any given system, all will have some sort of alien relic in it if you look hard enough- a crashed ship here, a resource cache there. nearly all have something truly substantial- more than a ship, an abortive colony or a wormhole gate or somesuch. some of those have something really big: a megastructure, full dead/zombie civilizations, etc
"nowhere without history, nowhere untouched or unaltered- an old cosmos..."
individual minds may well find themselves subsumed in hivemind cultures
concept for the disc: nation decides to Force Project and Show The Flag with a truly massive aircraft carrier style ship, with the rubric of "okay so if we have a ship that's yea big and the disc is x big then at wildly optimistic speed we should be able to go around the whole thing in just ten years!" (but actually the disk is ten times larger than they thought and the ship only goes half the speed it was expected to) so there's just this giant ekranoplan skimming the sea on slowly dying nuclear plants coming across various polities that they expect to bow and scrape to them but they're like "you have to understand that you're just a big boat we've seen those before"
but they should be able to circle the entire disc in just about 300 years... if they get their required every-twelve-year nuclear fuel replenishment, and if they can handle the gradually-changing atmosphere as they proceed along (which well they probably can, especially if the disc maintenance bots go "oh there's a ship, let's make sure they don't die")