Warning: The lore dump is strong in this one.
Back in the chapter introducing Tom Bombadill, we learned about the kings who died in the Barrow-Downs. Tom tells the hobbits that someone did some dark magic and rose the dead men from the grave, making the dead into wrights.

At first, I believed the Riders were dead kings from the Barrow-Downs, but I talked to my spouse about this and he thinks that the Barrow-Downs and the wrights in these parts were just flavor text to add to the fantasy.
My husband said, “The rings for the nine humans were distributed to them before they became wrights.” Which does make sense.
I’m at the Council of Elrond chapter, so my perspective is limited, but I will give out some snippets from what I’ve read so far. Now, at this point in the story, we haven’t heard a lot about the Riders, but we get some information from Gandalf and Elrond.
Gandalf told Frodo back when he was at the Shire that the “Nine he gave to Mortal Men, proud and great, and so ensnared them. Long ago they fell under the dominion of the One, and they became Ringwraiths.” If I didn’t watch the movies, I’d be confused about this.
Merriam-Webster defines wraiths as “the exact likeness of a living person seen usually just before death as an apparition.”
When Frodo woke up in Rivendell, Gandalf said, “Black Riders are the Ringwraiths, the Nine Servants of the Lord of the Rings.”
Gandalf also mentioned during the council of Elrond, that Sauron was the “Necromancer in Dol Guldur.” We know that the Nine are wraiths under control of Sauron, but I’d like to know who they are.

Later in the council meeting, Gandalf said that the Nine gathered under their fell chieftain, a “great king and sorcerer he was of old.” I’m not sure if this refers to Sauron or the king who stabbed Frodo back at Weathertop.
It’s likely this is the king who stabbed Frodo because why not just say Sauron’s name here? My question is who is this king?
Note: I’m not using any outside help including the movies as I write these entries. I’m only using The Fellowship of the Ring, The Two Towers, and The Return of the King books.
