Of all the Nazgûl, the Betrayer is amongst the lowest of Sauron's lieutenants, for even the Dark Lord is leery of placing faith in one who betrayed his kin so readily. 6th:The Tainted. Where the other Nazgûl were slowly swallowed by the taint of their rings, the Tainted gave himself wholly and willingly to Sauron. More @Wikipedia
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