Emperor's Children - Betrayal: Following the Cleansing of Laeren, the rot of corruption had begun to spread throughout the IIIrd Legion. Lord Commander Vespasian, one of two senior commanders within the hierarchy of the Emperor's Children, staunchly adhered to his Legion's ethos of perfection of honour, refusing to allow himself to fall to the rampant hubris and arrogance that had become more common within the ranks of the IIIrd Legion. Over the course of many months, Vespasian consulted other like-minded Battle-Brothers within the Legion, including 2nd Company commander Solomon Demeter, about his growing concerns and fears for the future of the Legion.Vespasian was present during the meeting between Ulthwé Craftworld Farseer Eldrad Ulthran and his Primarch Fulgrim upon the Eldar Maiden World of Tarsus. He had heard the dire warning presented to them of the Warmaster's corruption by the then-unknown dark powers of Chaos and the inevitable rebellion that would soon follow. The Primarch had rejected such accusations as outright heresy and ordered his delegation to attack the upstart Xenos.Lord Commander Vespasian reluctantly followed his Primarch's orders and destroyed Tarsus and the rest of the Maiden Worlds the 28th Expeditionary Fleet had recently encountered through Exterminatus. Weeks later, Fulgrim's fleet was ordered by the Council of Terra to rendezvous with the Warmaster's 63rd Expeditionary Fleet to inquire about reports of the their recent conduct and acquire information in regards to Horus's grave injuries acquired on Davin's feral moon. Vespasian was excluded from this delegation with the Warmaster, further demonstrating the growing rift between the Lord Commander and his Primarch Fulgrim.Following this delegation to the 63rd Expeditionary Fleet, Fulgrim announced to his senior commanders that he would lead a small force to join Ferrus Manus and his Iron Hands at Callinedes IV in the Callinedes System under the pretense of clearing it of an Ork infestation. The rest of the Legion would rendezvous with the Warmaster's 63rd Expedition at the Istvaan System to halt a growing rebellion.But the IIIrd Legion wasn't to fight alone, for they were to deploy alongside the Death Guard and the World Eaters. Though the men of his Legion cheered in adulation at the prospect of fighting with their brother Astartes, Fulgrim's amusement turned instantly to sorrow as he understood that, but for Vespasian's stubbornness, a great many of these warriors would have made a fine addition to the army of the Warmaster's new crusade.With such warriors fighting for the Warmaster, what heights of perfection would have been beyond them? Vespasian's refusal to allow his men to sample the heady delights of Fabius's chemical stimulants, or to undergo enhancing surgeries, had condemned the warriors once under his command to death in the Warmaster's trap of Istvaan III.He realised he should have disposed of Vespasian much sooner, and the mixture of guilt and excitement at the deaths he had set in motion was a potent cocktail of sensations. When the killing on Istvaan III was done, the chaff would have been cut from Horus's force, and they would be a sharpened blade aimed at the heart of the corrupt Imperium.Vespasian met his end after the operation conducted by the IIIrd Legion to cleanse Callinedes. The Lord Commander was denied audience with the Primarch, a most unusual occurrence, after numerous requests. A dark shroud had hung over Vespasian ever since the battle on the deep orbital of the Callinedes System. He felt obliged to act after he observed Solomon Demeter's 2nd Company being intentionally abandoned by both Captains Kaesoron's and Vairosean's companies.Within solar hours, the 2nd Company had been in transit to the Istvaan System to rendezvous with three other Legions to pacify the rebellious world of Istvaan III. Finally seizing the opportune moment, Vespasian confronted Fulgrim in his stateroom over the growing corruption and decay of the Legion's ideals that they had been founded upon. The Lord Commander discovered, much too late, the malign influence of Chaos that had held sway over his Primarch. With sibilant whispers of the daemon-possessed Laer sword urging him on, Fulgrim murdered Vespasian in cold blood by stabbing him in the neck with the Anathame.