Dark Eldar and Death
Its been shown a lot of times, as soon a craftworld eldar dies without their waystone, or its destroyed. Their souls is instantly consumed by Slaanesh.
But how does the Dark Eldar get around that particular fact? History is ripe with Haemonculi resurrecting deceased Druchii as long just a part of them was left.
My own speculation is that their habit of stealing souls essentially masquerades their own souls for a while, giving them a grace period in which to be ressurected. But as Path of the Renegade shows, a too old soul bought back might have a daemon hitching a ride. As was the case with El'uriaq.