Dragons neither want nor need many of the luxuries common in the development of other civilizations. As a simplified example, most breeds do not feel significant discomfort from inclement or extreme weather and find most indoor environments claustrophobic, and so have never needed to devote their considerable mental faculties to the development of advanced architecture.
Naturally, they support (perhaps a bit condescendingly) the needs of their vassal servants to do the same, but when the dragons control the funding and approval of such endeavors, technological advancement is understandably slow. In the thousands of years the Council and dragonkind has been in control of the isles, its vassal races have seen little development beyond the confines of their late medieval and early Renaissance level societies.
There is great development within those confines, however, and one should never underestimate the power that magic provides in replacing some of the creature comforts that more advanced societies enjoy. Furthermore, the spread of learning institutions, funded and governed by the dragons, is supported by all but the most tyrannical wyrms. Vassal races and their dragon masters are generally better educated and enjoy a greater standard of living than those who exist outside of Council society.
Dragons of Council society, regardless of their nation and clan, are distinct from their counterparts in other worlds of the multiverse. The dragon language has a well-developed written form, and Council dragons do not shy away from composing elaborate scriptures and treatises for distribution in libraries; these are, of course, copied down in smaller versions for consumption by vassals, who may find it quite troublesome to lift a seven hundred pound book bigger than themselves. Many dragons enjoy reading, and literature is traded amongst clans as vassals might trade in gold or grain.
Perhaps affected by their time among their vassals, some dragons even enjoy wearing simple garments or jewelry. A sash across the throat, a gem-encrusted gold chain, a claw glittering with rings, or even wing piercings are not unheard of for a dragon to wear. This separates them, they claim, from clanless “rogue” dragons who are more rough around the edges and cannot manage such luxuries.
The many centuries that dragons endure risk the onset of terrible ennui, and so some wyrms stave off their boredom with games, hunting, and other activities to sate their needs. Clan Jadress, for example, brings in much of its wealth by playing host to various gaming dens and the preparation of elaborate cuisines to fulfill any dragon’s appetites.
Of course, few dragons will admit they can fall prey to such mortal afflictions as boredom. Dragons are nothing if not proud and so sure of themselves as the pinnacle of creation, so ordained by the Ninefold Dragon. A vassal that speaks out of turn about their benefactors can expect to be devoured in a red dragon clan, and at the very least be visited with scorn and condescension by a silver or gold clan. How could a dragon be anything other than right?
On the subject of vassals, each clan and breed treats theirs differently. The culture of vassal sometimes affects dragon, and vice versa, so across the generations they often grow to reflect one another. The elves, dwarves, and gnomes that populate most of the isles alongside their masters have long recognized their place in the society, which even in the best of circumstances is that of second class citizens.
Naturally, metallic and gem clans tend to treat their vassals better, but this is not always the case. Stories of gold wyrms who exile dissenters, even well-meaning ones, for the simple crime of flouting the dragons’ decrees for the greater good are not unknown. Conversely, even brutal red and white clans realize the value of their vassals, even if they are eminently expendable. Clan Vermillion, for example, has a surprising system of meritocracy where even a powerful vassal champion can achieve great status in the clan -- provided they can continue to maintain it against the constant stream of challengers.
Regardless of clan or breed, vassals perform many of the tasks dragons cannot (or will not) perform. The claws of dragons, despite their relative dexterity, cannot weave nets or form pottery, or quarry stone. Emerald dragon philosophers correctly surmise that Council society, and even individual clans, simply cannot survive as they are now without the support, labor, and love (or fear) of their vassal servants.
The Human Menace
In ages past, the dragon slayers came and wreaked havoc across the isles until the dragons banded together to fight them. Though they were defeated after decades of warfare, the scars the humans have left on dragonkind are psychologically profound. Humans are the one thing that dragons truly fear, and that is never easy to admit.
Human tribes, long degenerated from their heyday as the dragon slayers of old, still dwell on the isles. These remnants of the abandoned or vanquished dragon slayer armies have no knowledge of their ancient and glorious past, and rarely rise above the status of nomads or savages. Occasionally, a charismatic human warlord will rise and raid vassal villages, and it is then that the dragons act to cull the herd.
Despite this, humans have proven remarkably resilient and difficult to excise from the isles completely. Somewhere over the eastern horizon, the rest of their race lives still. The dragons quietly offer prayers that they do not return.
The land of the humans, should it ever be visited, is a monster-infested wilderness dotted with crumbling kingdoms and decadent city-states. Human civilization never truly recovered after the grand crusade of the dragon slayers, even thousands of years later -- tyrants and petty nations rise and fall, with society never advancing beyond a perpetual dark age.
The ancient grandmasters of the dragon slayers live on, however, as monstrous undead lords in crumbling Gothic citadels on the fringes of known lands -- cursed by Great Io for performing the very duty he charged them with in days of yore, hated and feared by the rest of humanity for leading their kind to disaster in a failed crusade. Recruits are few and far between, usually criminals or other outcasts that find shelter from justice or the depredations of monsters in the dragon slayer citadels. The choice the grandmasters and their servants give them is simple: join the slayers, or join the dead.
Their land has its own dragons, of a sort -- degenerate drakes, sinuous linnorms, and inbred hybrids exiled from the Io’s Blood Isles centuries or millennia before. The dragon slayers continue to hunt and slay these creatures, a mere shadow of what they once were, but begrudgingly allowed to exist for this service they provide to the rest of their kind.
The dragon slayer grandmasters have not forgotten the Io’s Blood Isles or the dragons who dwell upon them. Even thousands of years later, they boil with hatred of the dragons and their manipulative creator, the Ninefold Dragon, who deceived them into being his tools and then abandoned them to suffering and undeath.