Elves and Ringwraiths

[Zigûr]

Originally Posted by Ivriniel

(Eol the Dark Elf was, for example, basically, a sex offender. He imprisoned Idril Celebrindil in his creepy tree house, and of that union Maeglin was born)

I think you mean Aredhel Ar-Feiniel, sister of Turgon, as the spouse of Eöl. Idril was the daughter of Turgon, and Maeglin's cousin.

Originally Posted by William Cloud Hicklin

It is interesting that the appearance of the Ringwraiths comes in the same entry as "Tar-Ancalimon takes the sceptre. Rebellion and division of the Numenoreans begins." Could one or more of the RW, when still visible "mortal" men, have been Sauronian agents in Numenor itself?

My general assumption was that the three Númenórean Nazgûl would have been Lords in Middle-earth, perhaps colonial governors of the local Haradrim and so on, but I suppose there's no reason to think that they might not have been primarily based in Númenor itself given how much transit evidently existed between Middle-earth and the Land of Gift at the time. The reason I mention transit is because I would argue that Sauron probably didn't go to Númenor to dispense Rings.
As you point out WCH, the Ringwraiths appeared in 2251, thirty years into the reign of Tar-Ancalimon (2221-2386). The shadow first fell on Númenor apparently during the reign of his grandfather Tar-Ciryatan (1869-2029). The One Ring was forged c. 1600, and Sauron acquired the Nine during the War of the Elves and Sauron (1693-1701). If Sauron seized and dispensed the Nine prior to or during the reign of Tar-Ciryatan then between the War and Ciryatan's death there is a healthy time frame of 168-328 years. Perhaps the Númenórean Ringbearers might have had some influence in the descent of the shadow upon Westernesse.
If I think about it, Númenóreans would in some respects be ideal people to provide with Rings: they already had abundant resources and power to turn to their advantage, and being an already longeval people, any Ring-granted longevity would be unremarkable and no cause for suspicion. That being said, Tar-Ciryatan's corruption might also have been observed by Sauron as an opportunity to put the Rings to work, rather than the Rings sowing the seeds of corruption. Indeed personally I am more inclined to support the notion that the corruption came before the Rings, as in my opinion it is more thematically effective if Sauron is the exacerbator, rather than the originator, of the darkening of Númenor.

If I might touch upon the Mouth of Sauron, incidentally, I don't think it's necessarily implausible for us to imagine enclaves of Black Númenóreans surviving in certain places, deep in Harad and elsewhere. This is pure speculation. I simply don't think the Mouth of Sauron could have been both a) extremely ancient, and b) not a wraith.