[Spoilers ?]
Not "whence the Inchoroi" but "who are the Inchoroi?"
This is out there, and in no means a defamation of anyone, simply a fan theory (like how I think How I Met Your Mother is actually a suicide note).
Could the Inchoroi be humans from Earth? Thousands of years of technology advanced? They have a nuke, which is pretty human, especially in a universe where geometry can straight murder you and your whole town, unless you have a (non) magic rock. They seem to be he prefect blend of science and religion. One that utilizes weapons of mass destruction (and weapons of light, or lasers, or whatever). They can manufacture and manipulate genes, which honestly is technology we can or will be able to do within this century. The ship is built from a mystery metal, and if a time traveler brought back a set of titanium golf clubs to 800AD, or Chobham armor...and a modern tank...it would be as wondrous to them as sorcery is to us.
Also, the fact that the Inchoroi are looking for 144k souls. That's the doctrine of certain door knockers, born in North America, and fearing the edicts of Popery.
Was the Three Seas born of humanity from Earth? Were Nonmen genetic experiments of such colonization just as the Consult was, sent to condition colonies for humanity that never came? Save for the Five Tribes of Men (weird the five tribes all kind of look alike).
Did Earth die and the last remnants of the dead planet arise in the Consult? The Nonmen being tools left to, their own devices? The fact humanity was largely isolated on the other side of the mountains, separate from the Nonmen lends credence to this. Technology and tactics are logical, they have the same flora and fauna as Ice Age Earth, which would be great for a species looking to settle on a new planet especially after 6 thousand years.
Hence, the last remnants of Earth are in the Consult, taking knocking on doors to a violent new level? I would have pegged the Mormons to be the last folks, but then again, not as many Mormons in Eastern Canada as the Western US.