I think Max was talking about 'strangeblood' individuals a few posts back, so this might not be a bad idea, but I don't think he listed djinn or dragons or even demons in the conventional sense as setting elements? (I did imagine that Devas/Nephilim could be distant descendants of some divine progenitor, for what it's worth, but that's pending approval.)
You could always declare that the curse of the Faceless is magical enough that they don't have to worry about conventional sustenance?
I have been wondering if there's some real-world mythological equivalent to the wilders, aside from the obvious nymph/faun parallels. Would the vedic yakshas work as nature spirits?