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human
[Warhammer 40k] How does each faction treat their prisoners of war?

I know that being a p.o.w in the 42nd milennium must be a fate worse than death, but how are captives treated by the Orks as opposed to, say, the Imperium, the T'au, or Chaos? How do Craftworld Eldar differ from Drukhari, Corsairs or Exodites in handling p.o.w's?

Furthermore, do Necrons or Tyranids ever bother with taking captives? I can't imagine the Tyranids doing this unless they somehow figure out dangling Space Marines or Tau captives around means luring more biomass to them.
gpt
The Imperium doesn’t take xenos prisoners. Heretics and traitors may be given a chance to repent before their execution. Prisoners of the Adeptus Mechanicus may be converted into servitors. 

Orks occasionally take slaves, who are used as brute labour, food, training targets, and general entertainment. 

Tyranids digest their prisoners, and recycle the biomass. 

Dark Eldar take prisoners for the specific purpose of torture, rape, and more torture, with a side order of horrific mad science experiments and occasional agonising poisons. 

Tau might give you a chance to join them, after appropriate reeducation. 

Craftworld Eldar have no interest in taking prisoners. They’ll either kill you or let you run away, depending on which is more convenient to their purposes. 

Necrons hate you for being alive, and will swiftly rectify that flaw. 

Servants of Khorne will enslave you, and work you to death or until they decide to add your skull to the Skull Throne. 

Servants of Nurgle will keep you for a while, then let you go. Probably near a densely populated area. It’ll be fine, although you should probably get that rash looked at. 

Servants of Slaanesh will do things to you which our vocabulary cannot adequately describe. Eventually, if you’re really unlucky, you’ll start to enjoy it. 

Servants of Tzeentch will take you prisoner or let you go, torture you or heal you, lie to you endlessly or reveal maddening truths. You will sense some dark purpose to their manipulations. You will try to understand this purpose. Pray that you fail.