In the fictional Warhammer 40,000 universe, The Black Legion is a legion of Chaos Space Marines united to one purpose and not fighting between their many legions. They are always brought together in great numbers when it is the will of their great Warmaster, Abaddon the Despoiler. Whenever the black legion is called it marks the beginning of another of Abaddon's Black Crusades.

The Black Legion were originally known as the Luna Wolves, they were the legion of Horus himself and in honour of Horus' great achievements the Emperor renamed the legion the Son's of Horus. After Horus' treachery and defeat however, the legion was renamed as "The Black Legion".

The Space Marines of the Luna Wolves Legion were created using human stock taken from the violent hive gangs inhabiting a planet called Cthonia. This planet allegedly existed in one of Earth's closest neighbouring systems. Being within reach even for non-warp spacecraft, Cthonia had been colonised, built upon, tunnelled and mined probably since the dawn of space travel. As such, all natural resources had been stripped away and used up millennia before, and the ancient mining technology had long since been rediscovered and removed by the Adepts of Mars. The planet that remained was largely redundant and abandoned, completely riddled with catacombs, crumbling industrial plants and exhausted mine-workings.

Horus, the only real primarch of the Luna Wolves, was the first of the Primarchs to be recovered by the Emperor, having been cast much closer to Terra than the others, and was found at a much younger age. As a result, Horus was for many years the Emperor's only son, and there was a great affinity between them. The Emperor spent much time with his protege, teaching and encouraging him. Horus was soon placed in command of the Luna Wolves Legion - ten thousand Space Marines created from his own genetic code. With these warriors to lead, Horus accompanied the Emperor for the first thirty years of the Great Crusade, and together they forged the initial expansion of the young Imperium.

Horus's own Legion had all the glory of being the greatest Primarch's personal guard, and they shared Horus's credo of fighting to be the best. Under his inspiring command, the Luna Wolves were always at the forefront of the latest campaign, pushing the boundaries of the Imperium ever wider, driving further and further into the galaxy and striving to conquer and liberate more worlds than the other Legions.

At its conclusion, the Emperor declared it the greatest victory yet for his mighty
Imperium and was said to bestow much praise upon the Luna Wolves and Horus, for their part
in the campaign. The most notable reward was the renaming of the Legion. The Emperor sent word that henceforth they would be known as the Sons of Horus, in honour of their Primarch.
Horus himself was given the title Warmasterr- now officially supreme commander of the Emperor's forces.

Before he could return to Terra to be officially invested with his new title, Horus apparently fell ill on a small feral world called Davin. During his convalescence, he took part in the induction ceremony of a warrior lodge on the planet. This was the Primarch's well-tried practice to develop ties with local populations - feral natives were more easily recruited into the Imperial fold when the 'Warriors from the Stars' had become brothers. However, this time was different. In the days that followed, Horus's officers detected a change in his character. It is now presumed that the warrior lodge was in fact a Chaos coven, which somehow managed to ensorcel the Warmaster.

The Primarch proceeded to introduce similar 'warrior lodges' into his own Legion, and then others under his command. Horus's fealty had changed; his Legion believe that he was actually possessed by a Daemon. Whether or not this is true, it is certain that he was now allied body and soul to the powers of Chaos, and he had a new vision for the Imperium with himself at its head.

The Sons of Horus, already fiercely loyal and proud of their Warmaster, had no hesitation. They quickly renounced their oaths to the Emperor and started to worship Horus and his new gods. The corruption spread to every organisation with which Horus had dealings, including a division of the Adeptus Mechanicus, and from there to the Collegia Titanica and the Legio Cybernetica. The other Primarchs, Horus knew like brothers, and was already well practiced at motivating them. Appealing to their pride, martial prowess and courage, while playing upon past grudges and favours, the Warmaster gained the loyalty of fully half the Primarchs. The war that followed was the most terrible in the history of the Imperium, and came close to shattering it forever. Space Marines fought Space Marines and Titans fought Titans as Earth was invaded, and the Emperor's palace itself was besieged and breached.


In the end, though, it was Horus who was slain, and with him died the rebellion. It was a traumatic and devastating blow for the Sons of Horus.

The Legion is a flexible fighting force, that can perform well and adapt quickly to any combat situation. It was trained to respond sharply and decisively to the tactical orders of its Warmaster and consequently the chain of command within the Legion was very efficient. This suffered significantly during the early years of exile when the Legion was leaderless, but Abaddon has done much to restore discipline, mainly through fear and horrendous violence inflicted on those that displease him. Horus's favoured doctrine of 'tearing the throat out of the enemy' by eliminating their high command in a swift strike, remains a well-used tactic.
Organisation

After the death of Horus, proper structure within the squads and companies disintegrated, and their later dispersal in various spacecraft further fragmented the Legion. Now warbands of virtually any size and composition can be found following Black Legion Champions - ranking officers from older times or newly emerged leaders who have won favour through their violent deeds. At times, such warbands rally together under the banner of a greater Champion or even Abaddon himself, for a major raid or incursion into the hated Imperium. However, loyalty to differing Chaos gods often leads to internal politics and conflict. Possession by Daemons is still considered highly favourable, and many members of the Legion have the honour of being hosts.

The overriding belief of the Legion prior to the Warmaster's demise was in the ultimate superiority of Horus and themselves. In continually seeking to prove themselves as the greatest Legion, they did indeed achieve most in terms of sheer numbers of worlds brought into the Imperial fold prior to the Heresy. Their defeat and exile was a crushing blow to the collective ego of the Legion. It has taken all the strength of character of their new commander, Abaddon, to restore the Legion's sense of pride and refocus on their ultimate goal - to overthrow everything which the false emperor of Mankind created.

The Black Legion has a colour scheme that is primarily black with gold trim.