Spirit Torment

Somewhere in Shyish, the Realm of Death, there exists a structure known as the Great Oubliette. It is a literal continent-sized underworld that serves as a jail for the souls that ESPECIALLY pissed Nagash off. Miles upon miles upon miles of dank, slimy, padlocked cells - think Azkaban from Harry Potter x1000. And going with that comparison, the guards - or dementors - of this prison are the Spirit Torments. They are Papa Bones' pet jailers, torturers, and enforcers of his petty-ass will. In life, they were especially pitiless jailers that, in contrast with the rest of the Nighthaunt, got a pretty sweet deal - they essentially just have to keep doing what they were doing, only on a much grander scale. It's almost like Nagash has a soft spot for overbearing sadists who are way too cruel to their prisoners, or something.

They used to stick to the Oubliette presumably doing their whole joy-sucking shtick until the Soul Wars began, at which point they became a much more common sight. This was probably because their unique ability makes them incredibly useful against Stormcast Eternals; that ability being to take souls and keep them imprisoned within their supernatural locks, so that they can be dropped off back at the Oubliette. The rub here is that Stormcasts, who usually go crying back to Azyr upon dying so that they can be reforged, also end up getting trapped in these locks.