An Age of Darkness has descended upon the galaxy. Horus Lupercal, Warmaster of the Emperor's armies, has turned against his gene-father and sent the Imperium spiralling into bloody civil war. Of the eighteen great Space Marine Legions, finest of all humanity's soldiers, fully half have sided with the traitorous Warmaster, while the remainder stand staunchly loyal to the Emperor. It is a war of brother against brother, Space Marine against Space Marine, which has seen the might of the Imperium's vast armies turned upon itself in a cataclysm of fire and blood.

The Rhino is the most widely used armoured personnel carrier in the Imperium. Based on ancient STC technology, the fundamental design is robust, reliable, and easy to maintain, with an adaptive power plant that can run off a wide variety of fuels, making it perfect for the wide-ranging armies of the Great Crusade – and the wars of the Horus Heresy. As such, the Rhino chassis serves as a basis for many other war machines, and these transports are produced in their thousands – several distinct patterns are in common use throughout the galaxy, with the heavily-armed Deimos being the most widespread amongst the Space Marine Legions.

Heavy Support Squads provide the Legiones Astartes with mobile, infantry-portable firepower sufficient to bring down hordes of enemy troops or smash armoured vehicles apart with withering hails of fire, combining devastating armaments with all the flexibility of a footsoldier. Heavy bolters are the largest bolt weapons available to infantry, unleashing a storm of shells that tear apart enemy formations, while missile launchers are prized for their versatility, offering a variety of explosive munitions suited to eliminating infantry, tanks, or aircraft.

Tactical Support Squads replace the utilitarian bolter of their comrades with more specialised weapons, enabling a Legiones Astartes strike force to act with even more versatility and engage a wider range of targets on its own terms. Each of the armaments used by Tactical Support Squads has its place – flamers are ideal for clearing bunkers, trenches, and urban zones, while rapid-firing rotor cannons see use against hordes of lightly-armoured foes. Meltaguns provide bursts of thermic energy for tank-busting, and volatile plasma guns can melt even heavily-armoured elites. Arcane volkite weapons – both the volkite caliver and lighter volkite charger – sear through targets with beams of thermal energy.

Ahzek Ahriman has the unique distinction of being both the first and last Chief Librarian of the Thousand Sons, and is the most gifted mystic among their already-formidable psyker corps. A respected commander even before his Legion's reunion with its missing Primarch, Ahriman's keen intelligence and talent in warpcraft soon made him Magnus' foremost apprentice, but his greatest strength is his indefatigable will. Ultimately, this determination would see him play a pivotal role in the Burning of Prospero – and walk strange and terrible paths long after the close of the Horus Heresy.

The Kratos Heavy Assault Tank is based on an Ancient Terran pattern fielded during the Unification of Old Earth, redesigned after the Emperor's treaty with the Lords of Mars to serve as the spearhead of the Great Crusade, a line-breaker and foe hammer. This grinding battle tank is all but impervious to enemy fire, and its steady, inexorable advance provides an indomitable core to any assault by the Legiones Astartes, enforced by a barrage of overwhelming firepower.

The Space Marine Legions of the 31st Millenium field a diverse and formidable range of genetically-enhanced warriors and advanced war machines, superior to any other military force in the galaxy. As an Age of Darkness falls across the stars and the fires of rebellion rage out of control, the armies that were used to forge the Imperium turn upon each other in an apocalyptic civil war – the Horus Heresy.

The Space Marine Legions of the 31st Millenium field a diverse and formidable range of genetically-enhanced warriors and advanced war machines, superior to any other military force in the galaxy. As an Age of Darkness falls across the stars and the fires of rebellion rage out of control, the armies that were used to forge the Imperium turn upon each other in an apocalyptic civil war – the Horus Heresy.

The Imperium stretches across countless worlds, a newborn empire on the brink of ultimate victory. Yet at the peak of this golden age of conquest, the galaxy has been plunged into an Age of Darkness. Horus Lupercal, Warmaster of the Emperor's armies, has turned against his gene-father – and the eighteen Space Marine Legions, once united in a Great Crusade to consolidate all humanity beneath the Emperor’s banner, are riven by betrayal. This is the Horus Heresy – the bloodiest conflict humanity has ever known, civil war on a galactic scale, in which superhuman soldiers clad in advanced armour turn devastating weapons upon those they called brothers. Where do your loyalties lie?

Praetors are the mightiest warriors and battle-leaders of the Space Marine Legions, second only to the god-like Primarchs in martial skill and generalship. Those that choose to march to war clad in Cataphractii Terminator armour place great value in its enhanced resilience, which can stoically weather even the heaviest of incoming fire. These hulking warlords stride into the thickest fighting, leading their warriors to victory across hundreds of battlefields.

Prideful and impetuous, Geigor Fell-Hand is a Thegn of the Space Wolves with a long record of valorous deeds. Yet despite his skill and fury as a warrior, Geigor's record as a commander is marred by a number of battlefield reversals – most notably the loss of his entire war pack while fighting alongside the Thousand Sons, after his allies retreated in the face of an Ork onslaught. Geigor harboured a bitter grudge against the XV Legion for this perceived betrayal – and leapt at the chance to punish them in the Censure of Prospero.

Tactical Squads are the mainstay of the Space Marine Legions, highly versatile infantry units that can attack or defend at will, assault heavily fortified positions, and take and hold strategic objectives – or simply slaughter the enemy – in almost any terrain or situation. All 18 Legions make heavy use of Tactical Squads in different ways – it is by the fighting power of thousands of superhuman warriors such as these, armed with deadly bolters and armoured for battle in the harshest of war zones, that the Imperium has beat a bloody path across the galaxy at the head of the Great Crusade.