It's by "IncubiLord" mosly on Warseer forum, so thank you IncubiLord. ;)

"A shadowy terror prowls the chill darkness between the stars. None can predict their attacks and few survive them. The Dark Eldar are expert at locating the vulnerable and the weak, and their devastating raids steal away entire generations and leave worlds devastated beyond recovery. These bloodthirsty corsairs care nothing for territorial gain or strategic positioning, their pirate fleets exist purely to bring slaughter and misery, stealing what they can and enslaving any being they encounter.
The Dark Eldar arose back in the distant reaches of time, during the cataclysm of the fall that all but destroyed the Eldar race. Possessed with the worst traits of selfishness and immorality, Dark Eldar are an embodiment of the debauchery and excess that laid low the once great Eldar race.
DARK MILLENNIUM: Dark Eldar
In the Dark Eldar exists the need to torture, maim and humiliate all other creatures. There is no pleasure other than that which is at the expense of others. There is no goal for the Dark Eldar that is not accomplished without pain and suffering for their prey. Grief and bloodshed are ends in their own right for the evil pirates of Commorragh.
PIRATICAL RAIDS
To survive the Fall, the Dark Eldar fled material space into the webway, a labyrinthine network of Warp tunnels that exists neither within realspace nor within the Warp. The Dark Eldar use the webway to move unseen across the galaxy, traveling where no fleet, no patrol, no listening stations can detect them. With warships appearing suddenly in low orbit and the warriors emerging directly from the webway onto the surface of their target world, the Dark Eldar strike with absolute surprise. As Well as raiding worlds, the Dark Eldar prey upon ships and convoys in the depths of space, and have even been known to strike all vessels lying under the watchful guns of a dockyard. The speed and viciousness of a Dark Eldar raid swiftly overwhelms any hasty defense and eludes any counter-attack. The Dark Eldar take what they want, slaying and slaving in a vicious whirlwind, before disappearing as quickly as they arrive, leaving nothing in their wake but ravaged corpses and mourning families.
AN ALLIANCE OF DEATH
Dark Eldar society has given rise to all manner of warriors and strange weapons of war. Most Dark Eldar warriors wield the terrifying splinter rifle, which shreds skin and flesh with a hail of razor-sharp barbs. Others wield weapons of arcane power, born of an ancient and twisted heritage. Alongside these warriors battle the Wyches, raised as stunningly skilled gladiatorial fighters in the arenas of death. For power and prestige, the callous and insane Haemonculi concoct exotic combat drugs and lead squads of twisted, altered creatures created in hellish laboratories.
The principle vehicle of the Dark Eldar is the Raider; a swift anti-grav skiff that carries a force of ruthless killers into the heart of the enemy. Ravager anti-grav tanks bristling with weaponry support the Raiders, along with lightning-fast Reaver jetbikes and howling (Hellions)
riding aboard soaring skybards. With pr(ecise attacks,) the Dark Eldar slay commanders, cut off (retreat,) and isolate their quarry.
TERROR AND POWER
It is a constant fight for survival and power (that drives) the Dark Eldar to their depraved acts. Hidd(en in the) depths of the webway lies the city of Com(morragh,) where most of the Dark Eldar make their (lairs. There and) in scattered enclaves throughout the webw(ay the Dark) Eldar try to outdo each other in power, we(alth, and) ruthlessness. Only absolute power guarant(ees their) survival, so Dark Eldar band together into (organizations) known as Kabals.
Many Kabals are simply a captain and his (crew made) of the violent street gangs that terrorize th(e entries to) Commorragh where the fleets arrive. Some (Kabals,) however, are powerful indeed. Through (wealth, trickery,) intimidation and alliance, the Greater Kabals (possess) influence that stretches into every aspect o(f Dark Eldar) society. The largest Kabals extort taxes from (incoming) fleets, sponsor Wych Cults and bargain wi(th strange) creatures such as the sinister, cannibalistic (Mandrakes) and the winged mercenaries of the Scourg(es. Among )
the Dark Eldar, there is one simple tenet:
The strong survive, the weak perish."
Note: The parts between brackets are guesses by the aformentioned forum member.