"Gothmog
Lieutenant of Morgul at the Battle of the Pelennor
Lieutenant to the Lord of the Nazgûl at the Battle of the Pelennor - he took command of the forces of Minas Morgul after the loss of his lord."
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Ok, I want to clarify some things for people:
Gothmog in ROTK was 100% for sure -- an ORC. You will now understand that this was no stretch of the screenplay writers for the movie -- that deformed orc leader was undoubtedly Gothmog.
The long lost name of the Witch-King?
Well, when the Witch-King, Lord of the Nazgul, destroyed the North Kingdom (Arnor), the last great refuge of the Dunedain that survived the fall of Numenor, the new Kindgom in its place that he ruled was what? the Kingdom of Angmar.
That's right --- without any other evidence to the contrary if you are looking to plant a name on the Witch-King -- then Angmar has got to be it.
The Witch-King, btw, was also of the same heritage as Aragorn - but from the "bad seed" tribe referred to as the Black Numenoreans -- the ones that got the gods angry enough to destroy Numenor in the first place.
The ORIGINAL Gothmog was indeed the prime Balrog, but he is long since dead by the time of the War of the Ring, and actually, it is probably safe to say that the Moria Balrog was probably the last remaining in existence before Gandalf finishes him off.
Now the 2nd in command of the Ringwraiths/Nazgul IS actually directly named in the writings of Tolkien, and his name was Khamul the Easterling.
Here is a very good "fictionalized" portrayal of all the Nazgul. I think this is taken from the ICE series of game supplements and I'm pretty confident that most of this, with the exception of Khamul, is complete fabrication when it comes to actual names and biographical details, but still, the manner in which these are done is so true to the spirit of Tolkien, I think you couldn't go wrong using this as a guideline when all else fails.
The Nine, the Nazgul
I hope what I've typed here is of help. I look forward to playing this Mod eventually.