After having learned that Curze had arrived to the Eye and made contact with him, Horus began to plan for a great gathering of his brothers, in order to rebuild the alliance that had nearly destroyed the Imperium and ushered in a new age for Mankind.
Horus knew that Magnus must already be there : the Thousand Sons had been the first to make their lair in the Eye after Prospero's destruction, and their sorcery would have make their retreat after the defeat of Terra quicker than that of any other Legion. There had been no sign of Magnus' children since the Siege, but the Warmaster knew that they must be there. There was nowhere else for them to go, and after surviving the Burning and the rebellion, Horus very much doubted there existed anything that could truly destroy the Fifteenth Legion once and for all.
He also knew that his brother Lorgar had fled to the Eye after he had humiliated and banished him from the war effort at Ullanor, due to his feeble attempt at killing Horus and replacing him as leader of the rebellion. In addition, the Urizen had been the first Primarch to physically journey to the Eye of Terror, long before the others had conceived of rebellion (save perhaps Angron, who had craved the Emperor's death from the very moment he had met their creator and be cheated of his own doom). Furthermore, Horus had heard from the daemons that had whispered in his ears through the last section of the rebellion that Kor Phaeron, Lorgar's adoptive father, had arrived in the Eye after his defeat at Calth and had claimed the daemon world of Sicarius in the name of his Legion. No doubt Lorgar had already made his way there, to be joined by the rest of his Legion.
Fulgrim's defeat at Guilliman's and Sanguinius' hands had echoed through the Empyrean, and Mortarion's orderly retreat to the Eye was known to the Sixteenth Legion. The Warp sung of Perturabo's great victory over Dorn, even if the Lord of Iron had been interrupted before he had been able to claim the Praetorian's life.
As for Alpharius … who knew. Even Horus himself had not known all of the Hydra's moves during the rebellion, and after the muster at Ullanor, there had been no sign of his brother Primarch, though members of the Twentieth Legion had taken part in the Siege, seemingly of their own volition. But the Warmaster did not doubt, even for a moment, that Alpharius would know of the gathering, and come if he so wished. Such was the way of the Alpha Legion.
And so Horus sent his call. Those Sons of Horus who had been Librarians before the rebellion had long since learned to throw off the limitations of the Edict of Nikaea, becoming full-fledged Sorcerers, and with their help the Warmaster sent forth his summons on the aetheric tides.
For the first time in years, Horus was forced to think like a diplomat, rather than a conqueror. Since the end of the Great Crusade, the Warmaster had put aside diplomacy, instead offering the systems he crossed a simple choice : submission or destruction. The overwhelming power and momentum of the rebellion had allowed him to dispense with the niceties, but now, with the armies he had gathered broken and his own defeat at the Emperor's hands – even though it had been more of a mutual defeat than a victory for any of them – things were different. He could not simply command his brothers to attend him and expect them to answer, let alone follow his orders in the Long War to come. There was to much baggage between them, too many grudges.
Horus knew that asking his brothers to come to Maeleum, the stronghold of his Legion, would be a poor diplomatic gesture, and so instead his message called for a gathering on what would hopefully be considered neutral ground by all Primarchs : the remnants of a dead Eldar Craftworld once called Zu'lasa, destroyed during its launch by Slaanesh. There, for the first time since they had met above the black sands of Isstvan V, the nine Primarchs who had betrayed the Emperor met.
As the host of the gathering, Horus was the first to arrive. The Warmaster came to the ruins of Zu'lasa in full regalia, wearing his black armor and fur cloak, holding Worldbreaker in one hand and the Talon on the other. The Eye of Horus was emblazoned upon his chestplate, a crimson and black orb that glowed with the same eldritch radiance that radiated from the Primarch's cybernetic cowl. He came alone, leaving his Mournival aboard the Vengeful Spirit, to monitor the movement of the other arrivals and keep watch for any sign of treachery.
For several hours, he walked the corridors of the dead Craftworld, taking in the traces of the desperate battle that had been fought by the Eldar as the daemons of Slaanesh swarmed the great vessel. Then he came to what had once been a temple dedicated to Khaine, the Bloody-Handed God of War that the xenos had worshipped before their entire pantheon was destroyed by the Dark Prince. The statue of the Avatar was still there, its pieces scattered across the room, each carefully defaced by the claws of the Neverborn.
Horus sat upon a fragment of the dead god's head, and waited for his brothers to arrive. Whether because they had answered his call promptly or because the Eye's time-warping effects were working in his favor, he did not have to wait for long, and they all arrived nearly at the same time.
Perturabo came with all the discipline one might expect from him. His fleet emerged from the storm in perfect formation, the Ironblood looming at its heart. The proud Gloriana-Class battleship already showed signs of its time in the Eye, as well as under the command of its newly ascended Daemon Primarch. Tendrils of living metal threateningly floated around it, and gun emplacements sprouted from vast sections of the hull that were covered in a mix of hardened flesh and machine.
The Lord of Iron came to Zu'lasa with eight of his Iron Circle. His transformation had removed the malady that had afflicted him since Fulgrim's assassination attempt on Iydris, and more : now Perturabo was taller than ever before, and radiated an aura of power that was second only to that of Horus himself. The Daemon Primarch went straight to the chamber where Horus was waiting, teleporting directly aboard the Craftworld using the new, Warp-touched technology his Legion was already developing in the wake of his ascension and their exile in the Eye.
'Perturabo. I am glad you arrived before the others. There is much we need to discuss in private.'
'Horus. Why did you call us ?'
'Because, brother, as you have shown us, our defeat at Terra does not mean we have lost the war.'
The Lord of Iron smiled. It was not a pleasant smile. It promised destruction and ruin, the annihilation of worlds and the drowning of hope in cold, unfeeling tyranny.
'I am listening.'
When the Night Lords arrived, the very Warp parted before them, recoiling from the madness of Konrad Curze. The Eighth Legion had come in force from Kerlazium. Thousands of Legionaries from the Tormentor faction had flocked to their Primarch, while the Long War loyalists had once again been tasked with ensuring the actual transportation of the Night Haunter. Aboard the Umbrea Insidior, flagship of the 1st Company, Konrad Curze laughed as the fleet travelled to Zu'lasa, absent-mindedly carving captive damned to shreds while thinking of all the potential futures he could see stretching from the coming gathering. Once the fleet arrived, easily twice as numerous as that of the Fourth Legion though not nearly as disciplined, the Night Haunter called five of his sons, seemingly at random, to accompany him as he went to the Craftworld. Three of the five were members of the Long War faction, while the remaining two had been falling further and further down into the corruption of the Warp. Only the presence of their Primarch kept these favored sons from turning on each other during the journey, such was the growing chasm forming between the Legion's factions.
Unlike his brothers, Magnus did not need to use a ship to travel. The Crimson King simply manifested himself on Zu'lasa, using his immense power and mastery of sorcery to transport himself and nine of his closest sons from the Planet of the Sorcerers to the Craftworld. Each of the nine Thousand Sons were powerful Sorcerers, chosen from among the few who had survived the disastrous Rubric of Ahriman with their minds intact.
Lorgar's flagship, the Abyss-Class Trisagion, came alone, its Geller fields inactive. Instead of being protected from the madness of the Warp by the ancient technology, the Word Bearers had elected to placate the Gods by crucifying thousands of slaves to the vessel's hull, binding their souls to their flesh with sorcery so that they could not simply die of void exposure. Left as playthings for the Neverborn, these unfortunate souls – all of whom were cultists of Chaos who had volunteered for the honor – had suffered untold torments. A few of the most resilient or unlucky were still "alive", transformed beyond recognition by the whims of the Warp. They would be harvested by the Word Bearers before the ship's next journey, to be either added to the Legion's horde of horrors, or to be dissected so that the will of the Gods may be divined from their blessed entrails.
The Aurelian came to Zu'lasa with his two closest, once-disgraced advisors : Kor Phaeron, his adoptive father, and Erebus, along with a group of seventeen figures in hooded black robes, all of them mortal-sized. While he was still mortal, he radiated the power of Chaos in a barely-controlled storm of energy that was contained only through a supreme effort of will. His golden skin glowed with an infernal inner light, and the sigils carved upon his armor shone with the same illumination.
The Death Guard of Mortarion was shrouded in thick clouds of flies, whose buzzing was somehow heard even across the void of space. The Endurance was accompanied by a scattering of lesser vessels, all of which bore the signs of Nurgle's affection for the Fourteenth Legion. The gunship that carried Mortarion and his Deathshroud to Zu'lasa was almost more insect than machine, and the fluids that leaked from its engines attacked the ground it landed on, creating a slowly expanding patch of black, wet rot identical to the ones left wherever the Death Lord stepped.
Angron's arrival was heralded by a great scream, and a wave of blood-red fire spread across the roiling clouds of Warp energy. The Conqueror emerged from the inferno, its once-white surface now the color of dried blood, the Daemon Primarch of Khorne standing on the vessel's hull, his bat-like wings spread wide as he drank in the raw energies of Chaos. Calling the Red Angel had been one of the most difficult parts of arranging the gathering, as Angron had never been one for formality, even before he had been stripped of the last shreds of his humanity on Nuceria. No one knew what had become of him after the Siege, but his continued survival was guaranteed, as he had become as immortal as any daemon upon his unholy transformation.
To make sure he would be there, Horus had called upon the ancient ties of loyalty that bounded him to his brother, and used the eight commanders of the World Eaters who had survived Skalathrax to amplify his summon. As Angron flew the distance between the Conqueror and the ruined Craftworld, these eight warlords departed from their ships, which had been waiting nearby. Since Skalathrax, they had ruled the Twelfth Legion under Horus' leadership in a joint council. Now, they returned to the side of their true master, the one for whom they had willingly inflicted the Nails upon themselves. Only they knew what transpired between them and the Red Angel when they met, but all eight of them were still alive when Angron reached the meeting chamber.
From the depths of the Craftworld, where the Neverborn had performed unspeakable acts upon the spiritual leaders of the would-be Eldar exiles, Fulgrim manifested in all his terrible glory. The White Naga slithered out of the warped bones and echoing nightmares of the dead, passing from his own realm through the stain upon reality that the daemons' deeds had permanently etched upon reality. Where he passed, the ghosts of the Eldar were dragged back from oblivion, manifesting as ethereal shapes that writhed in pain as they were forced to relive their last moments. Fulgrim smiled as he advanced, and softly sung to himself a melody that was as beautiful as it was discordant, adding to the suffering of the alien shades. The wraithbone shuddered and twisted at his presence, reshaping itself into the image of screaming faces and obscene daemonic figures.
Alpharius, or at least a warrior claiming that identity, was the last to make his presence known, though Horus knew he must have been there before any others – possibly before the Warmaster himself. The lord of the Hydra simply emerged from behind a broken pillar once all the other Primarchs were gathered, taking his place among them as if he had always been there. His brothers, both living and immortal, looked upon him with suspicion, but did not question or challenge him. He was alone, and carried no weapon greater than a bolter and a combat knife sheathed at his belt, yet he did not display any sign of nervousness as he stood among Daemon Primarchs and the chosen champions of the Dark Gods. Curze barked a laugh as his brother's appearance, and clapped, the talons of his gauntlets clashing together in an unpleasant ring.
So began what the historians of the Eye would, in time, come to call the Broken Conclave.