Adopt from the sensational CrimsonEclipse
Original at: https://www.furaffinity.net/view/45391042/
Flat chested version: https://www.weasyl.com/~darknz/submissions/2161559/
Nyx is a soul eater. Souls she consumes are stored in her breasts, each soul making them a bit bigger, sometimes you can see the little glowing soul balls floating around inside, perfectly content in such a comfy home.
The bodys of people whos souls she has consumed continue to live on, but as a thrall that is obcessed with serving Nyx and her ever growing breasts. Over time the thrall transforms into a goodra hybrid of the original body, hips widening, tail thickening, skin/fur oozing goodra goo etc...
Nyx can return a soul to a thrall body via a kind of "breast-feeding" to allow a thrall to perform a task requiring higher functioning reasoning. The soul returned to the body does not necessarily have to be the one that originally came from that body. This kind of swap leads to subtle behaviour changes to match the soul given. The thrall will perform the given tasks as efficiently and quickly as possible as the soul will be yearning to return to the comfort of Nyx's breasts.