Fulgrim

The Legion's history begins with the descent of the Primarch child Fulgrim to the resource-poor world of Chemos. Dependent on interstellar trade for food, and cut off from the rest of the galaxy by ferocious warp storms, strict rationing and improvisation could not prevent the slow death of the people of Chemos. When the capsule containing the infant Fulgrim plummeted to the planet, the scouts who recovered the child pleaded with the leaders of the settlement of Callax to spare the child's life, as orphans were seen as a strain on already stretched resources and normally put to death.

Named after a long-abandoned god of the people of Chemos, Fulgrim soon became a legend in his own right. At half the age of his fellow workers, he was able to fulfil his obligations to the continual running of Callax with ease. He quickly grew to understand the technology he had to work with, and began to modify it, increasing efficiency dramatically. By the time he was fifteen years of age, Fulgrim had risen from the rank of worker, to become one of the Executives ruling the settlement. Learning of the gradual deterioration of both Callax and all the other settlements of Chemos, Fulgrim decided that he would save his world.

Under Fulgrim's leadership, teams of engineers travelled far from their factory-fortress, reclaiming and repairing many of the far-flung mining outposts. As minerals poured back into Callax, Fulgrim supervised the construction of more sophisticated and energy efficient machinery. As recycling efficiency grew to the point where Chemos was producing a surplus for the first time in years, Fulgrim began to foster a re-emergence of art and culture, aspects of humanity sacrificed in the struggle for survival. The other settlements allied themselves with Callax, and fifty years after arriving on Chemos, Fulgrim was its sole leader.

Fulgrim is described by Garviel Loken in the book False Gods as being beautiful, pale to the point of albinism, with eyes so dark as to be almost entirely pupil and with shimmering white hair.

The Great Crusade

When the Emperor first arrived on Chemos, Fulgrim swore fealty to him instantly, and was placed at the head of his Legion. From the Emperor, Fulgrim learned of the distant world of Terra, of the Great Crusade to reclaim the sundered galaxy, and of his own origins.

Travelling to Terra to meet his new Legion, Fulgrim learned that an accident had destroyed the majority of the gene-seed designated for his legion, and without their Primarch, replacing it was a slow and laborious process. Fulgrim came to address the two hundred Space Marines of his legion, and the words he spoke were said to inspire the Emperor so much that he named the legion the Emperor's Children, and allowed them to bear the sign of the Aquila, the double-headed eagle that was the Emperor's personal symbol, on their power armour.

Fulgrim was anxious to make his contribution to the Great Crusade, but the comparatively small size of his Legion meant that the Emperor's Children were placed under the command of Horus and his Luna Wolves. Horus and Fulgrim grew close to one another while pacifying the Eastern Fringe. Eventually, swelled by recruits from both Chemos and Terra, Fulgrim was soon able to lead a crusade of his own, bringing countless worlds into the light of the Imperium

Horus Heresy

When Horus declared that he would no longer follow the Emperor, believing him to be weak and undeserving of the battles fought in his name, the Emperor sent seven full Legions to challenge the Warmaster, and destroy him and his followers if necessary.

Fulgrim and the Emperor's Children were the first to arrive in the Istvaan system, Horus' forward base, and Fulgrim met Horus in person, demanding a personal account of his actions. Instead, Horus was able to sway Fulgrim to his cause. Fulgrim's respect for Horus allowed Chaos to find its way into Fulgrim's heart, destroying Fulgrim's loyalty to Terra, and replacing it with burning desire to destroy the man who held humanity back from the perfection Fulgrim desired. Slaanesh whispered to Fulgrim, and Fulgrim accepted the promises of his new god.

The rot spread from Fulgrim to his lieutenants, the Lord Commanders of the Legion, then to company and squad leaders, and finally all but a bare handful of Marines followed Slaanesh and the Arch-Traitor Horus rather than the Emperor. Perfection became perfect hedonism. When the loyalist legions arrived in the Istvaan system, the Emperor's Children were at the forefront of the fighting, aiding in the massacre of their former brethren.

The time of Fulgrim's conversion to Horus' rebellion is not entirely clear, the recent book False Gods heavily hints of a pact between the brothers before the events of Istvaan, as Horus gifted Fulgrim with an alien weapon known as an anathame during a visit by Fulgrim to Horus' command ship shortly after the events of Davin. The anathame was stolen from the interex's Hall of Devices by First Chaplain Erebus of the Word Bearers, and is reportedly capable of killing even the Primarchs. This weapon wounded Horus on Davin, and it's been heavily speculated that this weapon was involved in Fulgrim's killing of his brother Ferrus Manus and the serious wounding of Roboute Guilliman after the Heresy.

Further, Galaxy In Flames suggests that Fulgrim is corrupt by the time of the novel's events. Inspired by a previous encounter with the alien Laeran, he has already commissioned Apothecary Fabius Bile to tamper with the Legion's gene-seed, creating monstrous abominations and enhancing marines like Eidolon beyond the original Space Marine template. Fulgrim is also complicit in the betrayal and slaughter of members of his own legion that are loyal to the Emperor alongside loyalist Death Guard, Sons of Horus and World Eater marines on Istvaan III. Horus himself notices a change in Fulgrim, noting that he has become more like a rake or a libertine than a warrior.

Horus' rebellion spread, bringing the entire Imperium into civil war. 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. Billions of defenceless civilians were used as experimental subjects in the effort to create ever-more powerful stimulants and pleasure-inducing chemicals, used to summon daemons, raped in countless cases (more explicitly implied prior to the Third Edition), or were simply tortured and killed to sate the bloodlust of the Legion.