Slaves in Commorragh come from all areas of the Galaxy and it is perhaps the worst place you could possibly be (there are a couple of non-Eldar contenders though). Of all the horrors of the 41st Millennium, little is worse than being taken alive by the Dark Eldar. Some say that it is better to be killed outright than to be hauled back to Commorragh. Not even the likes of Chaos can save your sorry ass once the Dark Eldar have made you their personal butt-slave.
The role of a slave in the battlefield (you should already know what Dark Eldar do to slaves on their off hours) is to act as cannon fodder, collect souls, and/or other menial tasks that Dark Eldar are too lazy/haughty to do (as seen in Dawn of War), such as sucking the Archon's dick on his personal pimp mobile. However, being a prisoner for some means little in the way of labor and many hours of boredom, perhaps on the deck of a Raider or Ravager whilst waiting for further punishment.
Usually, life as a slave is tough shit and the worst part is, the Dark Eldar try their utter best to keep you alive so long as you continue to suffer. Young human children are often considered the best types of slaves for the Dark Eldar, but Tau and even other Eldar are considered fair game.
Ork slaves are almost unheard of due to the fact that Orks aren't susceptible to pain and the very fact that they will most likely end up snapping the back of their owners more than anything else. But it can be done; there was a WAAAGH! of Orks that lived on a world where they had adapted to the toxic atmosphere. A Dark Eldar Archon needed them to build a statue because the poison chimneys his base was near kept killing his slaves. He managed to catch them, and likely keeps them drugged to ensure their compliance. It is unknown what the Dark Eldar think of Tyranids but chances are that they will try to find a way around it to make it possible to rape one. But considering the fact that Dark Eldar are the most likely army in eviscerating Tyranid players like there's no tomorrow, the possibility is more likely than you think. The only canon use they have for them is as beasts to fight and die in the arena; they even capture Synapse creatures despite the risk of luring a Hive Fleet to Commorragh meaning there is one weakness to the Hive Mind - alternate dimensions.
On the tabletop, Slaves are nothing more than decorations. We wish we were making this up but it seems that Games Workshop just made the Slaves so they could have a shitty excuse to model scantily clad women in chains. Unfortunately, due to GeeDub's overall lack of competence, the Slave models are ugly as sin. Seriously, their heads and faces are so disproportionate, that it is just plain awkward to look at, let alone jack off to it. How GW manage to fuck up even unarmed and simple modeled Slaves is a testament to their Fail.
Well...okay, maybe there are some uses for a Slave. Though of little practical use on the battlefield, you might even consider using them as Pain Tokens or Objective Markers. Sooooo......yay I guess?
|Forces of the Dark Eldar|
|Command:|| Archons - Haemonculi - Kabalite Trueborn |
Lhamaeans - Medusae - Sslyth - Succubi
|Troops:|| Beastmasters - Commorragh Slaves - Grotesques |
Hellions - Incubi - Kabalite Warriors - Mandrakes
Scourges - Wracks - Wyches
|Beasts:||Clawed Fiends - Khymerae - Razorwing Flocks - Ur-Ghuls|
|Pain Engines:||Cronos Parasite Engines - Talos Pain Engines|
|Vehicles:|| Raiders - Raven Fighters - Razorwing Jetfighters |
Reapers - Reaver Jetbikes - Venoms
|Super Heavies:||Ravagers - Tantali - Voidraven Bombers|