Space Marine Legions

The First Space Marines were produced using genetic material of the God-Emperor's twenty Primarchs. These were exceptional individuals, with great and varied powers. There were twenty Legions, each under the command of a Primarch. The Legions were incredible fighting forces, composed of Mankind's greatest warriors and armed with its most advanced weaponry and equipment. Each legion contained thousands of Marines, the only limit being the amount of Gene-seed the legion had for transforming humans.
During the Horus Heresy, in the 31st millennium, nine of the Legions were corrupted by the forces of Chaos, and rebelled against the Imperium. The traitors were eventually defeated but it was decided to divide the nine loyal Legions into smaller groups called Chapters, each consisting of approximately a thousand marines, to prevent any individual from ever again wielding enough power to pose a serious threat of rebellion. Each Chapter has some history back to one of the original loyal Legions.

Dark Angels
The first Legion to be created by the Emperor. The Dark Angels and their successors refer to themselves as the Unforgiven. Highly secretive, they hunt the "Fallen" Angels who sided with Chaos during the Horus Heresy.

White Scars
The White Scars have a Mongolian-inspired culture and fast-attack doctrines. The Chapter makes extensive use of bikes and Blitzkrieg-like tactics.

Space Wolves
The Space Wolves are fierce warriors with an organization that differs strongly to other chapters. Though their loyalty is unquestioned, they are known for their fiercely anti-authority attitudes.

Imperial Fists
The Imperial Fists were charged with defending Terra itself during the siege of the Emperor's Palace, thus being bestowed with one of the greatest titles ever.

Blood Angels
The Blood Angels and their successor Chapters have suffered from various gene-seed flaws, primarily the "Red Thirst" or "Black Rage" since the death of their Primarch. The Blood Angels excel at close combat and assault tactics.

Iron Hands
The Chapter's warriors display a high incidence of cybernetic modifications to their bodies and all recruits have the left hand removed and replaced with a cybernetic replacement.

The Ultramarines
The Ultramarines are rigid adherents to the Codex Astartes, and are the canonical Space Marine chapter from whose genetic material most new foundings are drawn.

Salamanders
Technically-adept warriors with a preference for short-ranged combat, the Salamanders favour heat-based weaponry.

The Raven Guard
The Raven Guard specialise in hit-and-run assaults using jump packs and extensive use of scout marines.