The Burning of Prospero

Not every catastrophe of the Age of Darkness was born of open treason. The Burning of Prospero was a tragedy in the truest sense: two loyal Legions set at one another's throats by pride, misjudgement and the manipulation of the Warmaster, so that the loyal-hearted destroyed the loyal-hearted while the true traitors watched and smiled. It cost the Imperium one of its most gifted primarchs and shattered a labour on which the Emperor had staked the future of humanity.

The Sin of Magnus

Magnus the Red, primarch of the Thousand Sons, was the mightiest psyker among the Emperor's sons and the master of a Legion of scholar-sorcerers who had turned the powers of the mind into an art and a science. Their gifts had already drawn suspicion. At the Council of Nikaea, the Emperor Himself had sat in judgement over the use of sorcery and forbidden its practice, fearing the doom that unsanctioned psychic power would invite. Magnus, believing his own wisdom equal to the danger, could not bring himself to obey. When he divined through sorcery that Horus had fallen to Chaos, he chose to warn the Emperor by the only means swift enough: a great psychic sending that tore through the very defences the Emperor had raised, and in doing so wrought a ruin far greater than the warning was worth.

The Broken Work

For the Emperor's secret labour, the reason He had withdrawn to Terra, was the construction of the webway project: a vast undertaking to open a safe road through the Immaterium so that humanity might travel the stars without trusting to the treacherous warp or the perils of psychic navigation. It was among the most ambitious works ever attempted, and its success might have freed mankind from the horrors of Chaos forever. Magnus's desperate psychic message smashed through the wards protecting that project like a stone through glass, breaching the barrier between the workings and the raw warp beyond. Daemons poured into the breach. The Emperor was forced to abandon His great work and turn all His power to holding the gates, and the road to a Chaos-free future was lost, not through malice, but through the arrogance of a son who thought he knew better.

The Wolves Unleashed

The Emperor, wrathful and grieved, resolved that Magnus must answer for what he had done. He summoned Leman Russ, primarch of the Space Wolves, the Legion He had always kept as His executioners, and charged them to bring Magnus to Terra to face judgement. It was a mission of arrest, not annihilation. But the order passed through the hands of the Warmaster's agents, who twisted it in the telling until a command to capture became a sentence of destruction. Horus saw his chance: to be rid of a loyal Legion and a loyal primarch at a single stroke, and to set two of the Emperor's most powerful instruments to breaking each other. The Space Wolves came to Prospero not to summon Magnus home, but to burn his world to ash.

Fire Over Tizca

The Space Wolves did not come alone. With them marched the Emperor's own praetorians, the Adeptus Custodes, and the anti-psychic Sisters of Silence, whose null presence smothered sorcery and left the psykers of Prospero blind and powerless. They fell upon the crystal city of Tizca, the shining jewel of the Thousand Sons, in a storm of fire. Magnus, wracked by guilt and half-convinced that he deserved the punishment, at first forbade his sons to fight, and the opening slaughter was terrible. Only when the destruction became total did the primarch rouse himself, and then the full and terrible power of the Thousand Sons was unleashed: sorcerers and Space Wolves tearing at one another amid the burning towers, two loyal Legions locked in a battle that should never have been fought.

The Bargain and the Fall

As his city died and his sons were butchered around him, Magnus faced a choice that would damn him forever. To save the remnant of his Legion he reached out at last to the powers he had always held at arm's length, and struck a bargain with the Chaos god Tzeentch, patron of sorcery and change. In exchange for salvation, Magnus and his surviving sons were spirited away from the ruin of Prospero and delivered into the Eye of Terror: saved from the Wolves, but bound now to the very darkness the Emperor had feared. The primarch who had broken the Council of Nikaea to serve the Emperor ended the day a servant of Chaos, his Legion transformed and his homeworld a smouldering grave. In the years that followed, the surviving Thousand Sons would be undone by a further sorcery of their own, their bodies unmade and their spirits bound to their armour, so that a Legion of scholars became a haunted brotherhood of ghosts. Horus had achieved everything he wanted: a loyal Legion pushed into damnation, and the Space Wolves and Thousand Sons alike diminished.

A Tragedy Without Villains

The Burning of Prospero remains the most heartbreaking episode of the Horus Heresy, for it was a war among the faithful. Neither Russ nor Magnus was a traitor when it began; both believed themselves the Emperor's loyal servant. The Space Wolves carried out what they thought was their father's will, and in doing so destroyed a brother-Legion and drove it into the arms of the enemy. The Thousand Sons suffered for a sin committed out of loyalty, and were remade into the sorcerous horrors the Imperium had always feared they might become. Above it all stood the Warmaster, who had turned pride against pride and loyalty against loyalty, and lost nothing. The lesson of Prospero, learned too late, was that in the Age of Darkness even virtue could be forged into a weapon, and that the road toward the Siege of Terra would be paved not only with treachery, but with the good intentions of the betrayed and the grief of brothers who woke too late to what they had done.