When Horus struck at the spiritual home of the Imperium, Terra, during the Horus Heresy, the seeds of what would become the Fists of Flame were firmly planted in those hallowed times.

As the defenders of the Imperial Fists Legion, under the venerable command of Primarch Rogal Dorn himself, worked to keep the traitors at bay at the gates of the Imperial Palace alongside the warriors of the Blood Angels and countless soldiers of the Imperial Army, they knew they were fighting a losing battle. It was only a matter of time before the onslaught of Chaos Daemons, traitor Space Marines and their vile ilk broke the defences open.

Fortunately for the Imperium, the Emperor opted to take the fight to Horus. Teleporting aboard the traitor Horus' vessel, the Vengeful Spirit, the Emperor was accompanied by a handful of Blood Angels and Imperial Fists.

Although Horus was eventually slain by the Emperor who himself received a mortal wound in return, the Imperial Fists survived their time aboard the Vengeful Spirit. Amongst their number, was the 14th Captain, Larn Judicar. When he returned to Terra, he was forever changed, having seen the horrors of chaos aboard Horus' flagship.

The Founding

During the aftermath of the Horus Heresy, the Age of Strife saw the Imperium scour the galaxy in search of the traitor, heretic and duplicitous agent and many thousands died at the hands of the vengeful Imperial Army.

With blade and sword, the traitor Legions were pushed further and further back, eventually driving them into the permanent Warp storm known as the Eye of Terror, where they remain even today, awaiting the time to reunite under a new black master and bring death the Imperium once again.

It was also during this time that Roboute Guilliman begun to lay down the foundations of the Codex Astartes, the holy tome which would see that the Legions would no longer exist and would be split into multiple Chapters, each roughly 1,000 Space Marines in size.

The Codex: Astartes

When his work was finished, the Imperial Fists Legion acceded to the Codex's strictures and broke down into a handful of Successor Chapters. Amongst their number, the Crimson Fists, Black Templars and the Fists of Flame.

Larn Judicar was placed in command of the newly founded Fists of Flame Chapter, and tasked with the duty of holding a small sector of space close to the Eye of Terror that would later become known simply as the Belt of Fire.

The mettle of the Fists of Flame were to be surely tested in the years that followed, for the vile spawn of Chaos emerged from the Eye of Terror time and time again, probing and looking for a weakness in the defences of the Imperium and each time, the Fists of Flame were there to drive them back, drive them out of the Belt of Fire with blade and purity of purpose.

It was also during this period of near constant warfare that the Fists of Flame were moulded, and Larn Judicar slowly eroded the concise organisation of the Codex: Astartes, instilling in the Chapter the ability to adapt and change and over time, this has led to them adopting the unorthodox organisation they bear today.