The Dark Eldar
Likewise affected by the Fall and the birth of Slaanesh, the Dark Eldar found a way to diminish the effect of Slaanesh's curse. In order to replenish their slowly withering souls, they feed upon the agony and suffering of others, which grant them regenerative powers as well as increase in strength. Provided they can feed often enough, they have effectively become immune to passing of time. However, such feeding only delays the inevitable, so the Dark Eldar have essentially exchanged a quick death for an eternity in hunger, constantly requiring more and more to prey upon, otherwise they'd slowly wither and become nothing more but soulless husks.
Driven by their hunger for pain and suffering, the Dark Eldar regularly emerge from their sub-realms, hidden in the Webway, in order to kill, destroy, plunder and enslave. They are constantly seeking for more slaves for their torture chambers, Wych arenas, weaponry factories and other purposes. Captivity by the Dark Eldar is a drawn out state of constant agony. It is said that being captured alive is the worst possible fate they could bring.