Brotherhood of the Phoenix - Fulgrim's Fall: The point at which Fulgrim and the Emperor's Children embraced darkness is not known. Some amongst those who serve the Emperor pointed to Fulgrim's cleansing of the dangerous xenos known as the Laer as the event that finally doomed him, as there are indications that the malign servants of Chaos used this event to ensnare Fulgrim and begin the rapid corruption of the Emperor's Children.It is believed that Fulgrim first fell from the Emperor's grace on the xenos planet called Laeran, officially designated by the Imperium as Twenty-Eight-Three, being the third world the 28th Expedition had brought to Imperial Compliance. Unbeknownst to the IIIrd Legion, the serpentine Laer species were corrupted xenos worshippers of the Chaos God of Pleasure, Slaanesh.Though the resource-rich Ocean World of Laeran would be of immeasurable value to the crusade of the Emperor, its alien inhabitants did not wish to share what blind fortune had blessed them with. They had refused to see the manifest destiny that guided Mankind through the stars and had made it abundantly clear that they held the Imperium in nothing but contempt. The IIIrd Legion's diplomatic advance had been rebuffed with violence, and honour demanded that they answer in kind.Fulgrim's 28th Expeditionary Fleet conquered Laeran for the Imperium, exterminating its hostile native reptilian species. Completely unaware of the real dangers he and his Astartes Legion faced on the Chaos-corrupted world, Fulgrim ordered the Emperor's Children and the other forces of the 28th Expeditionary Fleet to assault the planet and conquer it for the Imperium within a single Terran month, completely eradicating the Laer species in the process.During the final slaughter of that serpentine xenos race, Fulgrim and his Astartes discovered the great temple dedicated to Slaanesh that lay on the central floating coral island of Laeran. The Imperium, ignorant of the existence of the Chaos Gods at this time and holding to the extreme rationalism and atheism of the Imperial Truth, did not realise the significance of such a find or what they had really discovered.The expedition led by Fulgrim began to be unwittingly corrupted by the temple's potent and malign influence. After defeating the temple's fanatical Laer defenders, Fulgrim discovered what the Laer were so fiercely protecting -- at the centre of the chamber of the unholy temple was a circular block of veined black stone, and embedded within was a tall, single-edged silver sword with a gently-curved blade and a crude amethyst gem set in the pommel. This sword was not only a potent Slaaneshi artefact but also the physical vessel of a Greater Daemon of Slaanesh.Once Fulgrim had claimed the blade as his own, the Daemon within it began whispering in his mind and corrupting his soul towards the service of Slaanesh. Thinking the whispers in his mind was only his own subconscious speaking to him, Fulgrim began listening to what it offered. Eventually, he discovered these were actually the whispers of the Daemon that existed within the blade.After a lot of persuasion from his brother Horus, himself already corrupted by the Ruinous Powers after his mortal wounding on the plague moon of Davin, Fulgrim gave himself over to Chaos, and found his particular patron in the Prince of Pleasure, who offered the primarch a route to the ultimate perfection he so craved for himself and his Astartes, free of all morality and dependent upon the pursuit of ultimate self-obsession.Many of the IIIrd Legion's senior commanders that were with their primarch during the final assault on the Laer temple were similarly enraptured by the dazzling sights and strange discordant music as the cacophonous flood of sensations assaulted them with surges of light and noise.After their return to the Emperor's Children fleet in orbit, many of these affected Astartes continuously sought ways to stimulate their senses in an effort to recapture what they had felt in the Laer temple, both on and off the battlefield.As their primarch fell to the whispered temptations of the Daemon-possessed sword he had taken from the Laer temple, the Emperor's Children Legion continued its descent into a downward spiral of corruption marked by the affected Astartes' insatiable desires to satisfy their hedonistic wants.