Dark Aelfs of the Cult of Pleasure
The Slaanesh worshipping Dark Aelfs, that make up the Cult of Pleasure are everybit as evil and vicious as the ancient kin from the Old World. In many ways, even more so, with their talents for inflicting pain, married to the pusuit of pleasure and their mysterious skills of flesh crafting.
How and when their skin turned a dark purple/obsidian, is unclear. If it is experiments, their malicious ways personified or the corruption of She Who Thirsts.
The Dark Elves rarely go into battle themselves, but prefer to let the expendable mortal warriors, that appear to be flocking to their banner, or the beasts they twist or create, do the fighting.
But when they do go into battle, it is with devastating results for their enemies.