Istvaan III had two primary battlefronts: The Precentor’s Palace and The Siren Hold within Choral City. The images have been gathered from the Forge World’s Betrayal and the Horus Heresy Trading Card game. Unfortunately, most images do not have a description of where they are set. I’ve used my best judgement based on the descriptions from Galaxy in Flames. This guide has been produced as a visual library for basing ideas from your force.
The following excerpts are from Galaxy in Flames by Ben Counter
Choral City operated as the capital city of Isstvan III and was the seat of Imperial Governance.
“Further out from the palace and beyond the architectural perfection of the Choral City, vast multi-layered residential districts sprawled. Connected by countless walkways and bridges of glass and steel, the avenues between them were wide canyons of tree-lined boulevards in which the citizens of the Choral City lived.
The city’s industrial heartland rose like climbing skeletons of steel against the eastern mountains, belching smoke as they churned out weapons to arm the planet’s armies. War was coming and every Isstvanian had to be ready to fight.
“…of the Choral City as they had known it. Every scrap of living tissue was gone, burned to atoms by the flames that roared and howled in the wake of the virus attack.
Every building was black, burned and collapsed so that Isstvan III resembled a vision of hell, its tumbled buildings still ablaze as the last combustible materials burned away. Tall plumes of fire poured skyward in defiance of gravity, fuel lines and refineries that would continue to burn until their reserves were exhausted. The stench of scorched metal and meat was pungent and the vista before them was unrecognizable as that which they had fought across only minutes before.”
“Every time he let his mind wander outside the systems of the Dies Irae, he saw nothing but the tangles of charred ruins.”
“Once this place had been part of the palace, a handsome garden with summer-houses, ornamental lakes and a roof that opened up to the sun. Now it was a rubble-strewn ruin, its roof collapsed and only an incongruous decorated post or the splintered remains of an ornamental bridge remaining of its finery.”
“LUC SEDIRAE, WITH his blond hair and smirking grin, looked completely out of place among the rusting industrial spires of the Choral City.”
“Where Isstvan III had once been rich and verdant, Isstvan V had always been a mass of tangled igneous rock where no life thrived. Once there had been life, but that had been aeons ago, and its only remnants were scattered basalt cities and fortifications. The people of the Choral City had thought these ruins were home to the evil gods”
The Precentor’s Palace
The palace of old governance before Imperial Law. Ostentatious architecture that may be influenced by Xenos.
“The Precentor’s Palace, a dizzying creation of gleaming marble blades and arches that shone in the sun, opened like a vast stone orchid to the sky and the polished granite of the city’s wealthiest districts clustered around it like worshippers.”
“ON THE SOUTHERN SIDE of the palace, a strange organically formed building clung to the side of the palace like a parasite, its bulging, liquid shape more akin to something that had been grown than something built. Its pale marble was threaded with dark veins and the masses of its battlements hung like ripened fruit. From the expanse of marble monument slabs marking the passing of the city’s finest and most powerful citizens, it was clear that this was a sacred place.
Known as the Temple of the Song, it was a memorial to the music that Father Isstvan had sung to bring all things into existence. It was also the objective of the World Eaters. The word that the invasion had begun was already out by the time the first World Eaters’ drop-pods crashed into the plaza, shattering gravestones and throwing slabs of marble into the air. “
The legends told that Isstvan himself had sung the world into being with music that could still be heard by the blessed Warsingers, and that he had borne countless children with whom he[…]”
“Sheared sections of granite petals formed the cover behind which Loken and Tarvitz were sheltering, while in the rubble-choked dome below, hundreds of the survivors were manning the defences. Luna Wolves and Emperor’s Children manned barricades made of priceless sculptures and other artworks that had filled the chambers beneath the dome.”
“Now these monumental sculptures of past rulers lay on their sides with Astartes crouched behind them.”
“pointing through the ruins of the dome to the strange organic shape of the Warsingers’ Chapel adjoining the palace complex. The survivors had instinctively avoided the chapel and few of them had even seen inside it. Its very walls were redolent”
The Siren Hold
The seat of Imperial Governance. A product of Imperial brutalism, this concrete stronghold has familiar hallmarks of Terran architecture.
But no sight in the Choral City compared to the Sirenhold. Not even the magnificence of the palace outshone the Sirenhold, its towering walls defining the Choral City with their immensity. The brutal battlements diminished everything around them, and the sacred fortress of the Sirenhold humbled even the snow-capped peaks of the mountains. Within its walls, enormous tomb-spires reached for the skies, their walls encrusted with monumental sculptures that told the legends of Isstvan’s mythical past.
“He turned his bitter expression away and stared through the chapel window across the plaza still stained dark with charred ruins. Amazingly the chapel window was still intact, although its panes had been distorted by the heat of the firestorm, bulging and discoloured with vein-like streaks that reminded Lucius of an enormous insectoid eye.
The chapel itself was more bizarre inside than out, constructed from curved blocks of green stone in looming biological shapes that looked as though a cloud of noxious-looking fumes had suddenly petrified as it billowed “upwards. The altar was a great spreading membrane of paler purple stone, like a complex internal organ opened up and pinned for study against the far wall.”
“THE GREAT FORUM of the Mackaran Basilica was a desert of ashen bone, for as the virus bombs had dropped, thousands of Isstvanians had gathered there in the hope that the parliament house at one end of the forum would receive them. They had thronged the place and died there, their scorched remains resembling an ancient swamp from which rose the columns that bounded the forum on three sides.
On the fourth was the parliament house itself, befouled by black tendrils of ash that reached up from the forum. The building had been the seat of the Choral City’s civilian parliament, a counterpart to the nobles who had ruled from the Precentor’s Palace, but the prominent citizens who”
“Loken pushed through the sea of black bones, his sword ready in his hand as he forged through the thicket of bone. A skull grinned up at him, its burned and empty eye sockets accusing. Behind him, Torgaddon covered the forum beyond them.”
“The interior of the building had been protected from the worst of the virus bombing and firestorm, only a few tangled blackened corpses lying sprawled among the dark wood panels and furnishings. The walls of the circular building were adorned with faded frescoes of the Choral City’s magnificent past, telling the tales of its growth and conquests.
The benches and voting-tables of the parliament were arranged around a central stage with a lectern from which the debates were led.
On the stage, in front of the lectern, stood Ezekyle Abaddon and Horus Aximand.”