Angels of death in age of sigmar. Or rather fallen angels, and instead of a faction they'd be a subfaction to night haunt.
Where as the current night haunt range seems to be all mortals who are judged based on their life, the fallen angels are an extension of Nagash's psyche to go and judge what makes up the current range of night haunt, and are somewhat more elite than whats made up of the current night haunt range.