[Chronicles of Middle-earth] Mortal Greed and the Birth of the Nazgûl
Second Age, 1697.
Sauron sacked the Elven realm of Eregion and seized the Rings of Power. To dismantle the resistance of Middle-earth from within, over the following centuries, Sauron bestowed nine rings as irresistible "gifts" to the nine most powerful mortal leaders, sorcerers, and warriors across Middle-earth and the shores beyond.
Second Age, 2251.
As time passed, their frail mortal flesh could not withstand the unfathomable dark power within the rings. Around S.A. 2251, the physical forms of these nine kings entirely faded away, dragged forever into the Unseen Realm.
Their former glory turned to dust, they were reduced to invisible phantoms—the Nazgûl (Ringwraiths).
As long as the One Ring endures, these nine shadows remain immortal and undying, serving as the most loyal and terrifying enforcers of the Dark Lord's will.