Well it makes sense they were around for quite some time before they were destroyed, so the hillichurls are probably from another civilization, or maybe they came about also from dead gods(though probably not from the latter most likely from the former). whether they're from sal vindagner though I'm a little more doubtful on that I thought that they all died when the mountain essentially froze over when Celestia decided maybe they didn't quite like them too much.

+1