You know, I really like the concept here. It isn't wildly different from your standard demonic pact, but I don't really mind. I like how you took a relatively simple idea (sorcerous magic comes from a possessing spirit) and really fleshed it out to fit within your world. Well done, and thanks for the enjoyable read.
Ultimate power, a bit of madness, the risk of dying horribly... what's not to love about this.
I like the flavor that bleeds through. These aren't normal sorcerers who gather power through bound spirits. There is an entire ecosystem of ethereal creatures. It speaks to a larger, well-developed world, with enough similarities to standard fantasy to make it easy to grasp and enough uniqueness to set it apart.
Well, I was thinking of calling them something different. I chose to stick with Sorcerer simply because it was something people already knew, and it wouldn't be confused with the distinctly different "Wizard." But "Sorcerer" is simply the terminology that the Secta Arbite denotes to them. I'm sure the fearful populace has a number of colorful names to cakk them.
And to be honest PoisonAlchemist, I'm not entirely certain what happens when they die. I would assume that since the Prophet draws it's life force from the soul of it's host, when that soul vacates it can no longer sustain itself. However it is also bound at a physical and spiritual level as well, so the trauma of a "Real" death might simply kill the prophet as well.
I really like this different take on the sorcerer. I feel it should be linked to some sort of codex though since there seems to be an entire world hiding behind it. Why would a prophet wish to exist in the material plane? Do their kind have long term plans there? What happens when the sorcerer dies?
A note - simple math states that Kandolari populations will dwindle - a female needs to have more than two viable offspring that reach maturity to maintain a population. If infant mortality, war and disease play a large role, this number rises steeply.
Browsing once more: hair grows out of follicles, not pores.
Also, I would not have mutant 'castes' - mutation through its very nature is random. So, the same mutants are unlikely, unless the variant is caused by dormant genes that are easily activated; or unless the mutant breeds true, giving rise to a branching-off sub-species.
With their elfin appearance and colorful hair, they also confer an anime feel - I don't know if that's intended.
This is quite excellent for a first submission. Besides Echo's remark on what should be a rapidly declining population (maybe change it to 4 offspring, 2 of which might be "norma"). Besides that, this needs little changing, methinks. Well done, and welcome to the Citadel!