In the twenty-third century of the Second Age of Sun in Middle-earth there arose nine mighty wraiths who in the Black Speech of Orcs were named the Nazgūl, which is "Ringwraiths". And of all the evil servants and generals of Sauron the Ring Lord these Nazgūl proved to be the greatest.
It is said that the Nazgūl were once powerful kings and sorcerers among Men and they were each given a Ring of Power by Sauron. These Rings were nine of the magical nineteen Rings that Celebrimbor and the Elven-smiths of Eregion forged for Sauron.
For many years these Men used their Rings to fulfil their own desires, yet all were ruled by the One Ring that Sauron made. Though these chosen Men lived by the power of the Rings far beyond the span of ordinary mortals, their forms faded. By the twenty-third century they were wraiths entirely, and thralls that thought only of how they might serve Sauron the Ring Lord.
So they roamed the World committing terrible deeds. They wore great cloaks, black and hooded, and hauberks of mail and silver helms, yet beneath were the gray robes of the dead and their bodies were invisible. Any who looked on their faces fell back in horror, for nothing seemed to bear up helm and hood. Yet sometimes there appeared, where faces should be, the glow of two luminous and hypnotic eyes or, in rage and power, a red and hellish flame.
The weapons of the Nazgūl were numerous: they carried swords of steel and of flame, black maces and daggers with magical poisoned blades. They used spells of beckoning and spells of blasting sorcerous fire, and the curse of their Black Breath was like a plague of despair, and the curse of its terror froze the heart of their foes. The Nazgūl were untouchable to mortal Men, for arms could not unless blessed by Elvish spell and any blade that struck them withered and perished.
So for a thousand years of the Second Age of Sun the Nazgūl on nine black Horses swept over the lands of Middle-earth like a nightmare of terror. And in all that time, they fared in the war as Sauron the Ring Lord himself. They did not perish until the realm of Sauron's Mordor fell and the seven-year Siege of Barad-dūr was broken by the Last Alliance of Elves and Men at the end of that Age. Isildur, the Dśnedain lord of Gondor, cut the One Ring from Sauron's hand, and the Nazgūl with the Ring Lord were swept away to the shadows and the waste places in the eastern lands of the World where they had no form of power.
So, the Nazgūl were both formless and powerless for thirteen centuries in the Third Age of Sun. Yet the One Ring had not been destroyed and Sauron was able to make himself a shape again. So it was in the fourteenth century he summoned again his great servants, the Nazgūl out of the shadows. The nine Black Riders arose in the East and the greatest of these Nazgūl came to the north of Eriador, to the kingdom of Angmar and built a great citadel in Carn Dūm. He called forth Orc legions and the evil Hillmen of Ettenmoors. For more than six centuries there was continuous war in Eriador. The Nazgūl lord, who was at that time called the Witch-king of Angmar, made constant war against the Dśnedain of Arnor and out of Carn Dūm came much evil. One by one the great provinces and cities went down, until 1974, when the last province of Arthedain and the city Fornost fell to the barbarous hordes. Yet the Witch-king's possession of the Dśnedain Kingdom of the north was short-lived, for in 1975 his army was routed and destroyed by the Elf-lords Cirdan and Glorfindel and by Eärnur, the king of Gondor, at the battle of Fornost. But still the Witch-king and his master Sauron counted this as a great deed, for they were little concerned with the slaughter of Orcs and Hillmen, and the destruction of the power of the Dśnedain of the North in Arnor was indeed a great victory by the Dark Powers.
The Witch-king of Angmar, called the High Nazgūl, deserted the ruined lands of Eriador and returned to Mordor. And though Sauron was not yet come, but hid still in Dol Guldur in the darkness of Mirkwood, there were in Mordor the other eight Nazgūl who had come secretly three centuries before. In that time they had labored to rebuild the power of that land and had gathered Orcish hordes about them.
In the year 2000 the nine Nazgūl came out of Mordor to fight the Dśnadain of the south in Gondor, and two years later the eastern citadel, Minas Ithil, the "tower of the Moon" fell. The Nazgūl made this place their own and renamed it Minas Morgul, the "tower of Black Wraiths", and sometimes the Tower of Sorcery and the Dead City. The High Nazgūl, the Witch-king of Angmar, was now called Morgul Lord and wore a crown of steel. It was he who slew Eärnur, the last king of Gondor, and for a thousand years he made war on the Men of Gondor with both sorcery and the might of his army, and he eroded their power and their lands.
It was not, however, until the year 2951 that Sauron the Dark Lord declared himself and came to Mordor. It is said that Sauron feared to declare himself openly before that time lest someone possessed the One Ring, which would destroy him. And it was not until later still that even the wisest among Men knew that he commanded the wraiths of Morgul, and that these wraiths were the Nazgūl of the Second Age. In the year 3018 of the Third Age the War of the Ring had its beginning. For in that year Sauron learned where the One Ring was hidden and such were his desire that he sent all his Nazgūl to take it. Yet they were thwarted in their errand. When they came to the borders of Rivendell the nine Black Riders were unhorsed at the Ford of Bruinen and were driven away by the Elvish powers that commanded the river.
Yet they reappeared in still mightier forms, on steeds as dreadful as themselves. These steeds were the Winged Beasts for which Elves and Men had no name. They were ancient beings that had come into the World before the Count of Time began. Though they had beak and claw and wing they were not birds, nor even bats; they were serpentine beings like Dragons, yet older. They were made by Melkor, Sauron's master, in Utumno's foul pits, where serpent, Kraken and other vile creatures of hidden places had arisen. Fed on the cannibal meats of the Orcs and grown larger than all creatures of the air, the Winged Beasts carried the Nazgūl high over the lands with the speed of the winds.
Despite their might and fierceness, in the War of the Rings the Nazgūl were in deadly peril, because the One Ring was in the hands of their foes. In the battle of Pelennor Fields, the Morgul Lord, who could not be slain by the hand of Man, was brought to an end by the shield-maiden Éowyn of Rohan and the Hobbit warrior Meriadoc Brandybuck. Though eight of the Nazgūl remained they, too, were soon destroyed; as they rose to fight the enemy at the Black Gate of Morannon there was a great alarm within Mordor itself. Sauron commanded the Nazgūl to hasten to Orodruin, the Mountain of Fire, that is called Mount Doom, for there stood the Hobbit Frodo Baggins with the Ruling Ring. On their Winged Beasts the Nazgūl rushed like the north wind, yet to no purpose, because the Ring dropped into the fire of Doom and was unmade. In that moment Sauron and all his dreadful world were destroyed. As the Black Gate collapsed, the Dark Tower of Barad-dūr toppled, and in the midst of their flight the mighty Nazgūl fell shrieking in flames that ended them forever.