Honestly, my thought on the grey orcs--and interspecies hybrids in general--is 'scrap the lot'. They never really made sense the way they get presented, and making everything so closely related that anything can make babies with anything is just... eh. Only times I've ever liked it in D&D, really, are things like half-dragons. Because they're ridiculously magical and can shapeshift. 

Think I mentioned that I don't like the origins. Because it's just... weird. It isn't a race suggestion, it's also cosmology, setting backstory, decides the divine. It overreaches beyond a forgotten race to the point of just being... confusing? Seems better to not stick everything in concrete terms when it removes later options.

And I still have no idea what the Soul Contract thing actually entails, only that the random language mixing is a bit odd. And that it comes out looking like Latin for some reason. @_@

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Seeing as I wrote a lot on three of the others, I am not sure I should say anything on them. Also still in favour of tiny desert people and four-fingered steppe nomads. :P