~CHAOS
   The forces of Chaos emanate from the Warp, a swirling alternate dimension of
space. There are two ways in which Chaos forces can enter the material realm of
man. In many places, such as the Eye of Terror, the Warp spills over into real
space, creating a realm subject to the diabolical whims of Chaos. In these places
the foul forces gather to raid across the galaxy. The second way in which the forces
of Chaos can enter the world is by far more insidious and subtle. Corrupting humans
with falsehoods and promises of untold power, the forces of Chaos are often
summoned by the hideous rituals of deviants and their followers. On thousands of
worlds Chaos Cultists, human followers of the Dark Gods, plot and scheme for
rebellion.

~BIRTH ~OF ~THE ~CHAOS ~SPACE ~MARINES
   In the early days of the Imperium the Emperor's greatest Champion, the Warmaster
Horus, was beguiled by the Dark Gods and so led Titan Legions, countless thousands
of Imperial troops, and fully half of the Legions of Space Marines into revolt. The
Horus Heresy (as it came to be known) wrought catastrophic damage across space,
and the tremendous battles only ended after Horus' defeat at the Emperor's hands.
With their failure the once loyal Chapters fled into the dark realm of space known
as the Eye of Terror. But the story doesn't end there...