Dol Guldur

[William Cloud Hicklin]

But what intrigues me is the fact that Gandalf revealed who "the Necromancer" really is - and that is: did he overhear some captains' discussion - but I don't know from whichever they said he could be as sure as he was that Sauron is there - or did he see Sauron personally? He might took a peek through a keyhole into his throne chamber or something, but still...?

Easy- he felt a disturbance in the Force...

As to the W-K- that derives from his old title (Witch) King of Angmar. Although it's not out of the question that he or some other Wraith might have been ruler of a Black Numenorean realm, I doubt any BN colonists would have dared take the title of King so long as the House of Elros ruled across the Sea.

In fact, one might suppose that the Numenorean Nazgul were the last created- during Saurons captivity. But that wouldn't really leave enough time for the wraithing process to be completed.