Mortarion bowed curtly to the Emperor and began his oration.

“Brother Malcador claims that his issue has vexed the Imperium,” said Mortarion, his rustle-soft tones like the dry hiss of wind over aeons old sand dunes, “but he is wrong to believe there is anything complex about the issue. I have seen the devastation that unchecked sorcery leaves in its wake, worlds burned to cinders, populations enslaved and monsters unleashed. Sorcery brought these worlds to ruin, sorcery wielded by men who peered too deeply into dark places they should have known to leave well alone.

“We all know of the horror of Old Night, but I ask you this simple question: what brought about that galactic holocaust? Psykers. Uncontrolled psykers. The threat of these people is horribly real, and you all know the danger they represent. Some of you may even have seen it first-hand. The psy-engines and occullum of Terra search out the latent witch-genes among humanity and the Black Ships of the Silent Sisterhood trawl the stars for these dangerous individuals. Did the Emperor, beloved by all, build these machines for no reason? No, they were built to protect us from these dangerous mutants, using their powers in service of their selfish ends.

“ Thatis the difference. Where an astrotelepath or Navigator uses his powers for the good of others, allowing distant worlds to communicate or guiding the Expeditionary Fleets of the Imperium across the stars, the sorcerer uses his power for personal gain, for earthly power and dominance.

“Yes, the Imperium needs certain empowered individuals, but only those sanctioned and rigidly controlled. We know where power unchecked inevitably leads. You have all heard the stories of Old Night, but who among you has really seen what that means?”

Mortarion swung his manreaper, the deathly haft finally coming to rest upon his shoulder.

“The Death Guard have seen,” said Mortarion, and Ahriman wanted to laugh at his absurd theatrics. Though Mortarion played the role of the outraged righteous man, he was relishing his part in what he saw as the downfall of the Thousand Sons.

“On Kajor my Legion encountered a warrior race of humans that had fallen to barbarism. Extensive orbital surveys detected no trace of advanced technology, yet it took my Legion nearly six months to bring Kajor to submission. Why? They were savages, armed with little more than blades and crude flintlock carbines. How could such a feral race of savages hold the Death Guard at bay for so long?”

Mortarion paced as he spoke, the haft of the man-reaper marking time to his steps with a solid tunkevery step he took. “They held us at bay because they had fell powers and unseen allies. Every night, creatures of witchery hunted in the shadows and killed for the joy of killing. Blood red hounds stalked the darkness of the forests with savage instinct, and juggernauts of thunder broke our lines with every charge.”

The Death Lord paused a moment to let that last fact sink in. That anything could sunder a Death Guard formation was nothing short of a miracle. Though his desert wheeze was faint, no word of his narration escaped the attention of those gathered in the amphitheatre.

“My warriors have fought xenos species of every stripe and defeated them, but these were not creatures of flesh and blood. These were summoned into life by Kajori warlocks. These magi conjured lightning from their flesh, set fires with their thoughts and cracked the very earth with their shouted oaths! No power comes without a price, and with every victory we won, we discovered what that truly meant. At the heart of every city we captured, my warriors found vast structures we came to know as Blood Fanes. Each one was a charnel house of bones and death. We destroyed every one, and with each one lost, the strength of our foes waned. In the end, we ground down every ragamuffin force they sent against us. Surrender was not in their blood and they died to a man, destroyed by a ruling caste of warlocks who could not bear to relinquish their power. I still think of Kajor and shudder.”

Mortarion finished his tale in front of the Thousand Sons, the last syllable leaving his lips as he looked up at Magnus.

“Now I do not accuse my brother of such barbarism, but no evil begins with such monstrous acts. If it did, no sane man would ever consider it. No, it begins slowly, a small step here, a small step there. By such acts is a man’s heart turned black and rotten. A man may begin with noble intentions, believing that such small trespasses are minor things compared to the good he will do at the end of his course, but every act matters, from the smallest to the greatest.

“Tales of the Thousand Sons’ victories are legion, but so too are the whispers of their sorceries. In the past I have led my warriors into battle alongside those of Magnus and am well aware of what his Legion can do, so I can vouch for the truth of what Ohthere Wyrdmake says. It is sorcery. I have seen it with my own eyes. Like the magi of Kajor, the cult warriors of Magnus conjure lightning and fire to smite their foes, while their brethren crush their enemies with invisible force. I do not lie when I say that I knew fear that day, the fear that I had broken one army of warlocks only to find myself with another at my side.”

“You all know I distrust the institution of Librarians within the ranks of the Astartes, fearing for what the Thousand Sons are trying to seed within our Legions. No Librarians sully the ranks of the Death Guard, and nor will they while I draw breath. I have held my tongue until now, confident that others wiser than I knew best, but I can keep silent no longer. When Brother Russ and Brother Lorgar spoke of the battles fought to subdue the Ark Reach Cluster, I found myself compelled to break my bonds of silence, though it tears my heart to name my own brother a warlock. I cannot stand by and watch his obsessions drive him and his Legion into the abyss of damnation. Know that I speak not out of hatred, but out of the love I have for Magnus. This is all I have to say.”

Mortarion turned and bowed once more to the Emperor before returning to the box he shared with other warriors of his Legion.

Ahriman turned to Magnus, as he heard the high, sharp crack of glass. The heat of Magnus’ anger was radiating from his body. The primarch’s fists were balled on the obsidian coping, and Ahriman saw the volcanic stone had softened and run like the wax of an invocation candle. Blobs of what had once been glassy rock dropped to the floor where they shattered as their customary atomic structure reasserted its reality.

“My lord?” hissed Ahriman, all thought of Enumerations forgotten as a hot rush of imparted fury passed between them with a flash of psychic osmosis. He reached out to Magnus, his fingertips lightly brushing his primarch’s arm.

Magnus felt his touch and turned his gaze upon him. Ahriman recoiled from the depthless pit of his eye, the entire structure of it a wheeling lattice of unknown colours, as though every facet of emotion fought for dominance. Ahriman’s heart lurched at the anger and need for vindication he saw there, a furious battle between raging instinct and higher intellect. He saw Magnus’ desire to lash out at his attackers, the animal heart that cursed his brother for his limited understanding. Holding that back was the towering intellect that held court over his base emotions, a mind that had looked deep into the warp and seen it looking back at him.

In that moment of connection, Ahriman looked into the core of his primarch’s incandescent form, the incredible fusion of genius and chained aether bound in the creation of his incredible mind and body. To see the white-hot furnace of so mighty a being’s innermost construction was to stare into the heart of a newly-birthed star.

Ahriman cried out as he saw Magnus’ life unfold in the space of what could have been an instant or could have been a span of aeons. He saw discourses between luminous minds in a cavern far beneath the earth, and a wondrous figure descending to Prospero atop a golden mountain range. All this and more poured into Ahriman without heed that his mind was vastly incapable of absorbing such enormous quantities of memory and knowledge.