Possession

[Croaker]

Not if you define "soul" as you just did, as "the essence of your Realness". In that context, you might say that shadows have no souls, or very small ones.

RPGPundit

Yup, this might work for me. Talking "reality" instead of "soul"

But this is really interesting, you know?

Let's consider that reality becomes considered as "soul" in a religious version of Amber. Then, you could end up with the same justification for shadowling treatment that were used by our ancestors with slavery.

[RPGPundit]

In fact, I've used exactly that in the Courts of Chaos just about every time I've run Amber.
The courts of chaos has an "economic" system where power is based entirely on how much one has of the only thing of true value: your level of stable reality. Thus, Demons are second-class citizens to Chaos Lords, and common Shadows are slaves or food; though if a demon or shadow manages to build up their personal power and level of reality, they also go up in society.

RPGPundit