Perturabo - Horus Heresy: As the tragic outbreak of the Horus Heresy grew closer, it appears that Perturabo was put under ever increasing pressure, and as a result the fires of his bitterness were stoked to a raging inferno. Some have postulated that it was the Warmaster Horus who, time after time, engineered events and adjusted deployments to the primarch's detriment. For the Iron Warriors Legion the Horus Heresy came as the culmination and a series of reversals and fell tragedies that had occurred in the latter years of the Great Crusade, stalked the Legion and by their effect both deranged and twisted its Legionaries.Foremost of these had been the rebellion of Olympia, the seat of the Legion's domain in the Meratara Cluster and foundling home world of their Primarch Perturabo. With the death of the long-lived Tyrant of Lochos and Satrap of Olympia finally dead, the duplicitous and viperous politics of Olympia had severely developed into infighting and insurrection. The violence and division flared up worse than ever before because of the changes the Imperium had wrought on Olympia, and the discontent grew, due to generations of the planet's finest youth having been tithed for the Legion, never to return.The shocking start of the rebellion struck at the heart of the Legion and its master, and almost could not have come at a worse time; for over a year, the Iron Warriors Legion had been engaged in the almost single handed suppression of a major infiltration of the infamous xenoform known as the Hrud. All such actions in the history of the Great Crusade have proved costly both in terms of lives and the sanity of those who must fight such nightmares, and this proved no exception.Perturabo and the IVth Legion returned to their homeworld and brutally purged Olympia of its rebels city by city, overrunning the fortresses he had built and sparing no one who stood against him. By the time the massacre was over, five million Olympians had been killed and the rest put into vicious slavery to the Iron Warriors. Perturabo looked on at the remains of his homeworld in cold silence. Only once the great pyres were burning to cleanse the world of the heaps of corpses created by the IVth Legion's assault did Perturabo fully realise what he had done.The Iron Warriors were no longer the saviours of the Imperium; they had been destroying the alien Hrud one moment, and yet, in the next, they were committing genocide against their own people. With the cooling of Olympia's mass funeral pyres had come the realisation that nothing the Lord of Iron could ever do from that moment could ever atone for a worldwide genocide. His father would never forgive him so grievous a sin, but Horus had not only forgiven it, he had lauded his brother's thoroughness and dedication. Horus had sworn Perturabo never to feel guilt over what he had done to Olympia, but that was an oath easier to make than to live by.It was at this time that disturbing news of the outbreak of the Horus Heresy on the world of Istvaan III reached Olympia and new orders for the Iron Warriors came from Terra. Leman Russ and the Space Wolves had attacked Magnus the Red and his Thousand Sons Legion on their homeworld of Prospero at the direction of the Emperor and as a result of the deceit of Horus. Horus had turned Traitor with his XVIth Legion, the Sons of Horus, alongside some other allied Legions such as the Death Guard, Emperor's Children, and World Eaters.The whole of the Imperium was on the brink of an outright civil war. The new orders from the Emperor ordered the Iron Warriors to join with six other Loyalist Space Marine Legions to face Horus and his Traitor Legions on the world of Istvaan V. During the battle that followed the Iron Warriors, Night Lords, Word Bearers, and Alpha Legion all went over to the side of Horus, and almost completely destroyed the three remaining Loyalist Legions of the Imperial assault force -- the Iron Hands, the Salamanders, and the Raven Guard -- at the infamous Drop Site Massacre on that world.In truth, Perturabo and the other primarchs who turned Traitor on Istvaan V had already been seduced by the Warmaster and made their decision to stand with him against the Emperor, guaranteeing that the Traitors would field nine Space Marine Legions against the Loyalists.In the wake of the Drop Site Massacre, to celebrate Perturabo's decision to join his side in the conflict, Horus presented Perturabo with a Power Hammer called Forgebreaker that had been the personal weapon of the fallen Primarch Ferrus Manus of the Iron Hands, who the Traitor Primarch Fulgrim had beheaded during the Drop Site Massacre.The granting of this boon was the embodiment of a new pact between the Warmaster and the Iron Warriors' primarch, a gift from Horus to Perturabo intended to symbolise Perturabo and the Iron Warriors' newfound allegiance to the Warmaster rather than the Emperor. Fools claimed that Forgebreaker had sealed the pact between Horus and the Iron Warriors, but only Perturabo knew it was forgiveness that truly bound the Iron Warriors to Horus Lupercal.