Horus Heresy - Battle of Iydris: The Traitors' assault began five hours later, despite the full circuit of fortifications still being incomplete. The landing zone was almost surrounded, but the encircling walls had yet to meet one another. Layered rings of minefields and acres of razorwire spread from the outer faces of the walls, making the approach next to impossible for anyone without detailed maps and temporary dormancy codes. Leaving Warsmith Toramino and five thousand Iron Warriors to oversee the completion of the siege works and establish battery positions for the guns of the IV Legion's Stor-bezashk, Perturabo climbed to the cupola of his converted Shadowsword super-heavy tank, the Tormentor. The Iron Warriors had come in force and the Emperor's Children no less so. Like Perturabo, Fulgrim rode at the head of his army, a warrior god in impossibly bright armour. His brother might have ceded control of this mission to him, but Fulgrim was making sure he was still its figurehead.For all intents and purposes, the route into the citadel of Amon ny-shak Kaelis was undefended and their route unopposed. Ever mistrustful of the lack of defences, Perturabo had his Iron Warriors dug in, assuming a perfect formation outside the walls in a layered barbican that protected the Traitor Legions' line of retreat. Fulgrim’s host broke apart into individual warbands, ranging in size from around a hundred warriors to groups of nearly a thousand. Each of these autonomous groups appeared to be led by a captain, though such was the bizarre ornamentation and embellishment on each warrior’s armour, it was often impossible to discern specific rankings. Leaving the fortified bridgehead behind, Perturabo led his Iron Warriors and the Emperor’s Children contingent into the heart of Amon ny-shak Kaelis. The Sepulchre of Isha’s Doom was a monumental palace, sprawling and richly ornamented with bulbous mourn-towers and sweeping, ivory-roofed domes. As the column of Traitors pressed onwards towards the sepulchre, they were being silently and unknowingly observed by the Loyalist Astartes of the Sisypheum. Despite being outnumbered a thousand to one, the small force of Loyalist Legionaries devised a means to find another way into the massive sepulchre.As the two Primarchs neared their ultimate goal, Fulgrim kept pressing his stern brother with curt impatience to not linger. Perturabo took the time to study Fulgrim and his assembled host. His brother was sheened in sweat, but it was not perspiration that beaded his brow, Fulgrim was sweating light. Though it was faint, it was visible to Perturabo's gene-enhanced sight that saw beyond what even Astartes eyes were capable of detecting. He wondered if Fulgrim was aware of the radiance bleeding from him and decided he must be. His brother’s armour strained against his body and his features were drawn and tired, as though only by an effort of will was he still standing. His captains looked no better, like hounds straining at the leash. A number of Fulgrim's Lord Commanders' flesh was also suffused with a light similar to that enveloping Fulgrim, a deathly radiance that had no place within a living being. Perturabo did not trust Fulgrim one bit, knowing that inevitably he would be betrayed by his brother. The Lord of Iron pressed on, intent on bringing their quest to completion. As they neared their final destination at the heart of the sepulchre, the power at the heart of Iydris spasmed in hateful recognition of the followers of Slaanesh, known to the Eldar as She Who Thirsts, and awoke its guardians from their slumber.Thousands of crystalline statues threw off their previous immobility. They moved stiffly, like sleepers awoken from an aeons-long slumber, and the gems at the heart of their bulbous heads bled vibrant colour into glassy bodies that suddenly seemed significantly less fragile. This army of wraiths were the Eldar dead of Iydris. Soon both the Traitor forces outside the citadel as well as those inside were attacked from all sides by the revenant army. Like automata, but with a hideously organic feel to their movements, the Eldar constructs emerged in their thousands with every passing second. As Perturabo was busy fighting for his life, Fulgrim slipped away in the midst of the fighting. Realising where he had gone, the Lord of Iron stepped into the green glow emanating from the centre of the massive chamber. Perturabo understood that this was no elemental energy or mechanically generated motive force, but the distilled essence of all those who had died there.Perturabo descended downwards on an unending spiral towards a point of light that grew no brighter no matter how far he descended. The journey downwards was never-ending, or so it seemed until it ended. Fulgrim stood at the origin of a slender bridge that arched out to the centre of a spherical chamber of          incredible, sanity-defying proportions. The footings of the bridge were anchored on the equator, and a score of other bridges reached out to where a seething ball of numinous jade light blazed like a miniature sun. Iydris, it transpired, was a hollow world, its core this colossal void with the impossibly bright sun at its heart. Perturabo confronted his brother, realising that there was never an Angel Exterminatus. Fulgrim confirmed for Perturabo that there was no such weapon yet, for he was to be the Angel Exterminatus. Perturabo responded that his brother always did have an appetite for rampant narcissism, but this was the grandest delusion yet. Unamused at Fulgrim's explanation, Perturabo took a step towards his brother, Forgebreaker in his hand, intent on killing him. Fulgrim spoke a single word, its nightmare syllables tore at Perturabo's brain, causing him to stumble and drop to one knee. Fulgrim revealed the reason for his brother being drained of energy.When Fulgrim had arrived on Hydra Cordatus he had presented the Lord of Iron with a gift; a folded cloak of softest ermine, trimmed with foxbat fur and embroidered with an endlessly repeating pattern of spirals in the golden proportion. A flattened skull of chromed steel acted as the fastener. Set in the skull’s forehead was a gemstone the size of a fist, black and veined with hair-fine threads of gold. As they had made their way towards the heart of the Eye of Terror, the large gemstone at the centre of the skull-carved cloak pin had changed from black to a solid gold colour and pulsed with its own internal heartbeat. This was the maugetar stone, known as the harvester, which had slowly been draining Perturabo's strength and life force. With the Lord of Iron's sacrifice, Fulgrim would finally be able to achieve apotheosis. The two Primarchs ascended upwards within the shaft of light, emerging into the chaos that was happening within the heart of the sepulchre.