The armour of the Night Lords is dark midnight blue. Their
Primarch, Konrad Curze, was assassinated during the Heresy.
The Pre-Heresy Emblem of the Night Lords
The Night Lords were the 8th Chapter formed during the First Founding.
Their Primarch Konrad Curze - later to be know as Night Haunter- grew
up on the mining planet known as Nostramo, a world shielded from its
sun by a huge moon, and which therefore rests in almost perpetual
darkness. The days on Nostramo. such as they are, are only slighter
lighter than the pitch black nights, and the people of the planet grow
up with a deathly grey pallor. Suicide and depression are facts of
life on such a world, and were it not for the huge deposits of
adamantium found beneath the planet's surface, it is doubtful that the
world would be inhabited at all.
Violent crime was also a fact of life on Nostramo, until the young
Primarch took it on himself to wage a single-handed vigilante war
against the crime lords of the planet, taking on the name of Night
Haunter as one that would strike terror into the hearts of his
enemies. His methods were simple, vicious and direct: if you broke
his law, you died. There was no appeal, Night Haunter was judge, jury
and executioner.
The Great Crusade finally reached even this dark world, and the
Emperor was re-united with his dark-visaged Primarch. Night Haunter
was placed in command of the Night Lords. who quickly began to gain a
reputation for ruthless efficiency and an almost cynical disregard for
human life. Their Primarch's methods became the way of the Night
Lords themselves, and as long as they achieved their objectives, the
means just didn't matter. Soon stories began to circulate of massacres
and atrocities being committed by the Night Lords, some under the
supervision of Night Haunter himself, until finally the Emperor was
forced to recall Night Haunter to answer the charges against him and
his men.
But the Horus Heresy erupted before Night Haunter could return, and
then it quickly became apparent that all of the charges against him
and the Night Lords were true. Night Haunter had no hesitation in
joining Horus against the man he started to see as a weak-willed
hypocrite, and operating from a planet deep in the wilderness area of
space known as the Eastern Fringes he led the Night Lords on a
campaign of terror and genocide that has rarely, if ever been
equalled. Even after Horus had been defeated the Night Lords
continued to attack the Imperium, though increasingly without any
discernable plan or motivation for their steadily more murderous
attacks. Finally the Imperial Assassin M'Shen was able to infiltrate
Night Haunter's base and slay the Primarch, and with this act the
Night Lords quickly stopped being an organised threat to the
Imperium.
The survivors made their way to the Eye of Terror, where they continue
to take part in raids the Imperium. They do not appear to worship any
one of the Chaos Gods, and have become instead cynical, hard-bitten
and frighteningly ruthless warriors. They fight for the pleasure of
it. and for the material rewards it can bring, and not because they
worship some deity. This attitude means they look down on their more
dedicated brethren, be they fanatical Chaos Space Marines such as
Khorne Berzerkers, or zealous loyal Space Marines like the Dark
Angels or Ultramarines.
Taken from Codex: Chaos v2
When the Horus Heresy erupted, the Night Lords had no hesitation in joining Horus against the Emperor. The legion had already earned a reputation for ferocity and savagery and there is compeeling evidence that the Emperor was already planning to disband the legion before the Horus Heresy made such action impossible. In any case, once they had sided with the Warmaster the Night Lords embarked on a campaign of terror and genocide that has rarely, if ever, been equalled. Even after Horus had been defeated the Night Lords continued to attack the Imperium from their homeworld deep in the wilderness area of space known as the Eastern Fringes, though increasingly without any discernable plan or motivation for their steadily more murderous attacks. Finally the Imperial Assassin M'Shen was able to infiltrate the Night Lords' base and slay their Primarch and with this act the Night Lords quickly stopped being an organised threat to the Imperium.
The survivors made their way to the Eye of Terror, where they continue to take part in raids on the Imperium to this day. All of the evidence appears to indicate that they do not worship any of the Chaos gods and have become instead cynical, hard-bitten and frighteningly ruthless warriors who fight for the pleasure of fighting and the material rewards it can bring. Some reports imply that this breeds a contemptuous attitude toward their more dedicated brethren, be they fanatical Chaos Space Marines such as Khorne Berzerkers, or zealous loyal Space Marines like the Dark angels or Ultramarines. Taken from Codex: Chaos Space Marines v3