system
Given the following post, respond as if you're commenting on Reddit:
human
[LOTR] How long does it take for someone to become a ringwraith?

"They were once men, great kings of men. Then Sauron the Deceiver gave to them nine rings of power. Blinded by their greed, they took them without question, one by one falling to darkness."

So nine great kings of men receive rings as gifts from Sauron. Dwarves and Elves also received rings, so this is presumably before Middle Earth knew that Sauron was a servant of Morgoth. How long does it take before they become the horrifying demons in the iconic black cloaks that we know and fear? What exactly is the process involved? Do they slowly start looking more like Gollum before eventually taking their poltergeist form?
gpt
It's never stated exactly, but it seems to take quite a long time from the perspective of a normal mortal human. Wearing one of Sauron's rings (not just the One Ring) extends normal lifespans far beyond natural limits, and all of the Nazgul were kept on their mortal thrones far longer than they had any right to be. Their transformation occured at different rates as well:

> And one by one, sooner or later, according to their native strength and to the good or evil of their wills in the beginning, they fell under the thraldom of the ring that they bore and of the domination of the One which was Sauron's.
> 

 It's said that the Nazgul as we know them first appeared about 700 years after Sauron first forged his rings. So it's probably a process of centuries for a living mortal man to become an invisible wraith. And it's assumed that their slow degradation into his servants included a loss of their physical form as they slipped further into shadow, which would mean they all once had a terrifying gollum-style appearance. If only for a brief time in the context of their new existence.