As Czumneth sculpted the realm, she meant for it to be a paradise, a palace of her own to rival that of her absent master. She left much of Uglu in it, with much of the realm becoming a dark, mist-shrouded land, empty save for the glowing cracks of power that resulted from its traumatic birth – the Riven Chasms. But at the center of the small chunk of realmstuff, Czumneth sculpted a shining palace, which rose towering into the coruscating cacophony of coloured chaos that was Chaos. Its spires stabbed like phallic members into the void, while its circumvallation grew akin to a sculpted monument to pleasure. Indeed, the entire estate, with its indulgent mockery of an opulent mortal’s castle, became a hedonistic monument to sin and vice, and a mammoth tribute to perfection and ambition. Dubbing this new structure the Cyrenaic Citadel, Czumneth and her coterie of Keepers settled within. It is where she held court in the manner of a true Pretender, her seat of power from whence her and her nobles could strike out and spread Czumneth’s worship and excess.

Of course, no realm within that warping Chaos is free from its own quirks, and above the phallic spires of the Citadel and the Ugluan fog-lake called Hâli, the astronomy of the world was perhaps one of its most unique features. The twinned “suns” of Carcosa are black gaping voids, light-sucking holes of emptiness that whirl among the chaotic colors of chaos – the Black Stars. The moons, too, coil around themselves in physical impossibility like spherical ouroboroi – they have since been dubbed the Coiled Moons.

Aside from the City itself, these features – the Synder-crystal core, the glowing Riven Chasms, the opulent Cyrenaic Citadel, the fog-lake Hâli, the twinned Black Stars, and the impossible Coiled Moons define the sub-realm. 

Carcosa is a city as much as it is a realm. After its foundation, flickering realmgates – Carcosan Gateways – entwined the realm with the other realms in a complex and often shifting web. The strongest and most reliable connections are with Uglu, given that it is Carcosa’s parent realm and most proximate (as far as such words have meaning in the Realm of Chaos). Other gateways are scattered across other realms – and some are more reliable than others. One fact unites all of them, however – they are influenced by the Glistering Goddess of the realm to which they lead, warped by Her excess and modeled unconsciously in Her role. Invariably, they all sing the siren song of Slaanesh.

And it was this siren song, this soul-dirge, that called most of the mortals to Carcosa. Mortals, first a few, then more, then a hundred, perhaps, poured through the Carcosan Gateways that tenuously tethered Carcosa to the nearby realms. Some, perhaps, were driven by a need for space, or a flight from war, or perhaps were attracted by the luring song of the daemons that lived in the Cyrenaic Citadel. The most industrious, however, were the ones that arrived as explorers, infected by a desire to know, to experience, to see new things and places. Driven by ambition, these pioneers and colonizers could not help but enter the unknown realm-gates formed by Carcosa’s riotous birth, and could not resist being attracted to the mighty demonic citadel that appeared on the other side like a towering divinity in its own right.

Gradually, over the months, a village popped up, even a city. The process was gradual – food was difficult to come-by, and the water tainted with an unexpected elixir that sent the drinkers into manic frenzies, exhausting them in moments. Still, the attractiveness of the demonic realm brought in all sorts of people unable to resist its mythological status it had attained from the first explorers who returned through the gates. Gradually, industrious and clever as mortals are, the unnoticed family groups and small villages around the Cyrenaic Citadel figured out how to treat the water, to preserve much of the energizing effect without harming the imbiber. They learned to harvest the fog of Lake Hali, the great lake of cloud. They discovered how to hunt harpies, the serpentine and easily-trained Steeds, and the poisoned-tongued Cavorters that roamed the outlands beyond the palace walls.

But ever the palace was silent, its doors shut, the daemons inside entertaining themselves, and paying only little heed to the mortal insects that gathered against their abode like wretched bacteria. Even when the influence of the land tugged at their minds, and the effulgent but unseen radiance of the daemons compelled their worship, the mortals were ignored. Even as they carved symbols and built temples, influenced by the titanic, glowing etchings in the very ground upon which they stepped, the mortals were ignored. Even as they cried out to the mysterious being in the citadel, droning in chants and ululating in ecstacy, the mortals were ignored.

Only the most exceptional of mortals could earn Czumneth’s attention, and only the most excellent of those could earn her favor. Very few mortals were thusly successful, but a few of note have achieved such notice from the Glistering Goddess.