What lead to the disappearance of decency among the Emperor’s Children and made them walk the path of terror and destruction?
Via our good friends at Lexicanum
When the events that led to the Horus Heresy erupted, Fulgrim rushed to the Warmaster’s side, attempting to reason with his old friend. Instead, Horus seduced him, playing upon his love of flawlessness to weaken Fulgrim’s loyalty to the Emperor.
Although Fulgrim initially resisted and wanted to speak out against Horus, the weapon he had taken from the Laer temple actually contained a daemon of Slaanesh. This daemon had been whispering to Fulgrim since he picked it up and weakened his resolve to the point where Horus was able to sway him.
The rot spread from Fulgrim to his Lord Commanders, then to company and squad leaders, and finally all but a bare handful of Marines followed Slaanesh rather than the Emperor. The remaining loyalists, led by Saul Tarvitz, a Captain of the Emperors Children, fought bravely on Isstvan III but were eventually overwhelmed as Horus, and the three Primarchs who had already declared for him wiped out those forces they believed would remain loyal to the Emperor. The Legion then gleefully proceeded to aid in the destruction of the arriving loyalist legions.
After the fighting on Istvaan III, Fulgrim entered the Heresy proper with approximately 50,000 marines. They fought alongside the traitors in the Dropsite Massacre. The Emperor’s Children saw heavy fighting with the Iron Hands and Fulgrim slew their Primarch, Ferrus Manus. Some elements of the Emperor’s Children loyal to the Emperor remained, with at least one warband of them forming the Death Eagles.
Some time after Isstvan V, The Perfect Fortress erected by Fulgrim in a strategic key system, was taken by the Raven Guard by luring the self-reliant Emperor’s Children out. The whole Emperor’s Children garrison was destroyed. Later, the Legion accompanied Fulgrim along with Perturabo and the Iron Warriors to the Crone World of Iydris, where Fulgrim would achieve Daemonhood.
After the events on Iydris, the Emperor’s Children devolved into disparate warbands. While most accompanied Fulgrim as he rendezvoused with Horus or undertook his own adventures in the Warp, several warband leaders arose who undertook their own sadistic raids into Imperial territory. A third of the Legion remained under the control of the Eidolon, which attempted to destroy the White Scars both at the Kalium Gate and the Catallus Rift.
All trace of decency amongst the Emperor’s Children had vanished by the time they partook in the Siege of Terra. While other Traitor Legions assaulted the Imperial Palace, the Emperor’s Children embarked upon a spree of terror and gratification amongst the helpless citizenry of Terra. Millions of defenseless civilians were slaughtered and rendered down to create endless varieties of drugs and stimulants, countless thousands more dying to provide the Legionnaires with more direct and cruder pleasure.
