Voice; Private
They were killed by a species on my World called the Heartless. Once the Heartless takes the person's heart, the body divides up to become both a Heartless and a Nobody. [He points to the drawing of his Dusk again.]
But. Not everyone has the chance to become a Nobody. Only those with the strongest will power can move on to that stage. And if they end up in this white and warped form, then they're perfectly obedient partners to the end.
Long story short, pal, in a place with constantly fluctuating happenings and smart-aleck wardens, they'd be pretty damn useful.