Fate of the Nazgul?

[radagastly]

maybe i didn't explain before, Nazgul were evil, its torture to remain in limbo, so as a punishment to the Nazgul, Mandos forced them to remain in limbo.

I still don't agree. I understand the idea of punishment for evil men, but their souls are still those of men. Mandos has neither the power nor the authority to hold them within the circles of the world when it is time for them to depart. Only Eru knows what reward or punishment may await them once they leave.