[Meneltarmacil]

Let's see what we've got here.

One Easterling and three Numenoreans would still leave five wraiths unaccounted for. As for the Witch King, I don't think Tolkien ever mentioned where he was originally from, only that he was sent to Angmar after he became a ringwraith. So he might be one of the Numenoreans or from somewhere else entirely. I think a couple of them are probably from Harad, and it's possible that one of the ancestors of the Rohirrim (who were living in the upper vales of Anduin at the time, as I think I remember) may have been one.

This leads me to an interesting theory: I think that the Witch King may have been from the line of kings that eventually led to Eorl the Young. Before moving to Rohan, that race of people originally lived in the upper vale of Anduin, in the foothills of the Misty and Gray Mountains. The Witch King, after turning ringwraith ,was sent to command Angmar, a region that included part of that area. If Sauron wanted to control that area, I think that he'd probably send someone familiar with the land. However, this is only speculation since we're not given much information about where the Witch King was from. And in fact, Angmar includes more territory to the west that the early Rohirrim wouldn't have gone into.