Even long before the coming of the Exarchate and the Illuminated, the peninsula was a land shared between two peoples. In the hills and the valleys, the forests and the meadows, there were humans above and hedgehogs below.
Look beyond the quills and whiskers. The greatest distinction between humans and hedgehogs is what's euphemistically referred to as "The Kiss of the Worm". Without it hedgehogs can't develop properly. They do not gain their intelligence, their size, or their posture, remaining snuffling runts, barely above beasts. These unfortunates are called 'little siblings'. Sometimes they're made deliberately, as a sort of contraception. Sometimes they're accidental, when the Kiss doesn't take.
Misunderstanding of the Kiss has led to terrible strife in the past. Humans, who lacked the Kiss, were believed by some to lack a crucial part of their soul, and so were enslaved and hunted for the medicine of their livers. Humans in turn did not recognize the sapience of the little siblings, and the mystery of the Kiss aroused suspicions and conspiracies, the most innocent of which was that hedgehogs burrowed under farmer's fields to steal their turnips. The universalist teachings of the foreign faiths (universal divinity, for the Illuminated, and universal servitude, for the Exarchate) put the final nail in this conflict, which in any case had been dwindling for centuries as expanding populations brought the peoples into closer contact.
Among humans, hedgehogs rarely occupy obvious positions of power. They cannot interbreed with aristocratic bloodlines. The power they possess tends to be the sort that's less respectable, yet can't be denied: as merchants, clergy, members of artisanal guilds, even criminal organizations. Hedgehogs are looked down upon for eating insects, but because they do they make superb guerilla soldiers. Their natural inclination to digging and resistance to the toxins and stale air underground also make them effective miners.
There is a royally-commissioned group of prospectors, all hedgehogs, who officially are tasked with finding gold and silver for the royal coffers. Unofficially, they are royal spies with an excuse to be present on anyone's land.
Though hedgehogs can eat insects right out of the undergrowth, this is generally seen as a regressive behaviour, best left for little siblings. In hedgehog cuisine insects have endless preparations: spiced, roasted, mashed into paste, liquefied by spiders then imbibed, and so on. Something that can be felt still wriggling for a moment after being swallowed is the most desirable texture. Hedgehog feasts can include columns of ants marching right into diners' mouths, led and sweetened by lines of sugary paste, and brine-tarts with leeches swimming within. Roots and tubers are also enjoyed.
Hedgehogs have much lower alcohol tolerance than humans, and find being drunk less pleasant. Their drug of choice is the inner bark of trees infected with a particular sort of fungus, which is chewed over hours for a mild, dissociative high.
The necessity of the Kiss of the Worm has largely limited hedgehogs to the peninsula, though not for lack of their trying. There are many warren-colonies on distant shores, a few still sustained by immigration, but most abandoned and become abodes of monsters. The hedgehogs' "Worms" are difficult to transplant. There are even legends of an ancient hedgehog nation that dug right under the sea bed, living there in bubble-cities to this day.
With their fur and quills, hedgehogs have less need for clothing, but no less desire to display their status and fashion sense. Clothing is either made so that it will not be punctured by their quills, in the form of scarves, shawls, and aprons, or loosely woven so that quills can poke between the weave without ruining it. Quills too can be dyed by painting around quilling skin, the paint taken up and into the quills as they grow*, the patterns thus made denoting family, birth order, and vocation. The wealthiest warriors have eyelet doublets tailored to fit so that the holes of the eyes let every one of their quills through cleanly. As colours can be hard to distinguish in the darkness beneath the earth, things like scent, variations of temperature and texture, and the sound of rustles are emphasized and appreciated instead. The same preferences apply to hedgehog art. The most beautiful hedgehog architecture is grown instead of built, carefully arranged shoots and roots carrying stones up out of the soil over decades.
Their dead are buried in familial tomb-chambers, and their quills turned into pens used to write solemn music and ancestral prayers. Their children are frightened with stories of jovidies, giant monsters like something between a hawk and a weasel, demons of the empty air that can dive down and wriggle through a warren like furred lightning, gobbling up everyone inside in an instant, and of bloaters. Jovidies are rare enough that they've faded into folklore. Bloaters are unfortunately a real and regular menace.
There's a disease that causes the space between a hedgehog's skin and flesh to fill with buoyant gas. It's uncomfortable, but easily treatable. Some ne'er-do-wells deliberately seek out infection with it, letting it progress until they swell up like living balloons. This lets them commit bizarre acts of banditry, and then float away from any pursuit. These hedgehogs are called bloaters.
* Don't do this with real hedgehogs I don't think it would work.
