Chaos Space Marines

During the Horus Heresy, the terrible Imperial civil war that pitted Space Marine on Space Marine, there appeared two factions. They were the Imperium of Man, led by the Emperor and championed by the righteous and powerful Space Marines, and the ruinous powers of Chaos, a dark force led by the four Chaos Gods and spearheaded by the Warmaster Horus, once the Emperor's most trusted friend, son, and adviser before he was corrupted by the promises and lies of the Ruinous Powers. Chaos was defended and advaned by Warp daemons, human heretics and the dreaded Chaos Space Marines. Former Space Marine, they were turned into traitors to the Emperor by the powers of Chaos. Their power armor twisted under the influence of Chaos energies to embody their new allegiance, and the Chaos Space Marines now fight for everything they were forbidden to have before. Wealth, riches, power and pleasure.

History
The background shown in both Codex: Space Marines (Haines and McNeill, 2004) and Codex: Chaos Space Marines (Chambers et al, 2002) states that the Chaos Space Marine Legions represent nine of the twenty original "First Founding" Legions of Space Marines who fought in the Great Crusade for the Imperium of Man. At this time Horus, Warmaster of the Imperial forces and Primarch of the Luna Wolves Legion (which was renamed the Sons of Horus in his honor before the onset of the Horus Heresy), was corrupted by Chaos and instigated the galaxy-wide Imperial civil war known as the Horus Heresy.

After the death of Horus at the hands of the Emperor in orbit above Terra and the end of the Heresy, the remnants of the nine Traitor Legions along with the other former Imperial forces that had joined Horus and now served Chaos escaped into an area of the galaxy where the Warp actually bled over into realspace that was known as the Eye of Terror. Due to the nature of Chaos, and the temporal instability of the Warp, the very same Chaos Space Marines who had revolted against the Emperor continue to fight against the Imperium today, having effectively been granted a tortured immortality by the Ruinous Powers.

The Traitor Legions have kept their old names, with the exception of the Sons of Horus who were renamed the Black Legion by their new leader, Abaddon the Despoiler. Besides Horus, two other Chaos Primarchs were killed during or shortly after the Heresy (those of the Alpha Legion and Night Lords). The six surviving Primarchs have since been transformed into Daemon Princes by the Chaos Gods they serve. These daemonic Primarchs rarely take part in the affairs of their Legions or any part of the Warhammer 40,000 universe. Some of the Legions have pledged a singular loyalty to one of the four great Chaos powers. The closest thing to a leader that has appeared among them is Abaddon the Despoiler. Abaddon is the only Chaos Marine since Horus to be able to command the loyalty of all nine Traitor Legions, and has led thirteen Black Crusades out of the Eye of Terror against the Imperium of Man.

Differences - Chaos & Loyalist Space Marines
The Chaos Space Marines have the same genetic origins as the Space Marines, and thus have the same physical power. Due to their allegiance to Chaos, veteran Chaos Marines can be suffering from extreme mutations. Chaos Marines are also virtually immortal, whereby their millennia of experience afford them levels of mastery with advanced battlefield skills and tactics that younger Space Marines may not yet have. (A joke amongst gamers is that it has taken the Chaos Marines several millennia to work out that using a knife as well as a bolt pistol gets them an extra attack.)

They are equipped with the power armor and weapons they had when they initially betrayed the Imperium, which are broadly the same as those used by current Space Marines (although some differences now exist with jump packs, helmets, etc). The current setting of the Warhammer 40,000 game is about 10,000 years after the Horus Heresy, and, while the Imperium has made some minuscule technological advancements, Chaos Marines have far more limited access to the handful of new inventions that have appeared on the galactic scene. In general, anything developed since the Heresy is unavailable to them unless it has been captured; for example, the Iron Warriors are known for capturing and using Imperial tanks. While Chaos Space Marines have older technology, they compensate for this by having access to daemons and daemonic technology, as well as the unbridled power of the Warp.

Because the Chaos Space Marines have all traded their souls to Chaos, they are extremely fearful of death after which their souls will be consumed by the Ruinous Powers, much as Slaanesh has done to the Eldar. The Chaos Gods do not truly care for their Chaos Marine servants, and will gladly see them tortured for all eternity within their realms in the Warp for their own pleasure. Worshipers of Khorne are cursed to feel eternal rage, children of Nurgle will be forever consumed by despair, those who choose Slaanesh as their patron will be tortured until the end of time, and servants of Tzeentch will find insanity as their souls undergo a constant change in form. In theory, those who choose to serve Chaos Undivided are either shared or fought over by the gods in the afterlife. Only the promise of eternal life as a daemon prince reassures the servants of Chaos. This fear of death, however, does nothing to slow or halt the vicious might of the Chaos Space Marine armies.

Chaos Space Marine Legions
Each of the nine Chaos Space Marine Legions fights using a different style of warfare; also, four of the nine are dedicated specifically to one of the four major Chaos Gods. Codex: Chaos Space Marines (Chambers et al, 2002) includes the current rules for fielding a Chaos Space Marine army in a game of Warhammer 40,000; it also includes rules for fielding any of the nine specific Legions.

The nine Chaos Marine Legions are (in order of their Founding):


 * Emperor's Children
 * Iron Warriors
 * Night Lords
 * World Eaters
 * Death Guard
 * Thousand Sons
 * Black Legion
 * Word Bearers
 * Alpha Legion

There are also many normal humans and mutants who serve Chaos as cultists, and they are often used by the Chaos Marines to bolster their ranks. These traitors, mutants and heretics are collectively labeled the "Lost and the Damned". Rules and background for these forces can be found in Codex: Eye of Terror (Chambers et al, 2003).

In addition, since the Horus Heresy, some Second Founding Space Marine Chapters have been corrupted in one way or another by Chaos. Very little background information has been provided about these Chapters, and no specific rules exist for them, allowing players to adapt other rules to represent their forces. According to the records of the Inquisition's Ordo Malleus, approximately 50 Chapters have turned renegade in the ten millennia since the Horus Heresy. Examples include the Sons of Malice, the Damned Company of Lord Caustos, the Violators, the Thunder Barons, and the Astral Claws (known as the Red Corsairs since their rebellion).

The Forces of Chaos
The Forces of Chaos is an all-encompassing term that includes the Chaos Space Marines and all the other beings and entities who serve the Ruinous Powers of Chaos and often make war upon the Imperium of Man and the many other intelligent races of the Milky Way Galaxy. Among their number are included human and alien Chaos Cultists, Traitor Imperial Guard, Traitor Titan Legions, Chaos Space Marine Traitor Legions, Chaos Spawn, daemons of every kind and power level and countless other foul beings too horrific to be mentioned here.