Today's Date in the Shire
The Fellowship of the Ring remains in Lothlorien.
Fun and Games
Walk to Rivendell
Malbeth the Seer
"Nine he gave to Mortal Men, proud and great, and so ensnared them. Long ago they fell under the dominion of the One, and they became Ringwraiths, shadows under his great Shadow, his most terrible servants." (LR, I, 2)
The terror of Sauron's Ringwraiths, called in his Black Speech the Nazgūl, was still thought to be distant when Gandalf described them like this to Frodo, but what had been just a rumour of a past fear soon hit the Shire in form of the Black Riders.
When Sauron as Annatar together with the Elves of Eregion forged the Rings of Power, he gave nine of his rings to lords and kings of Men, in order to bind them to the Ruling Ring he intented to make. Deluded by their greed and will to power, they accepted, and used the Rings too often to be able to escape Sauron's ensnarement, and so they faded slowly into the world of twilight, abandoning their physical form, and yet not dying.
Therefore, they were then wraiths, forever bound to the One Ring, and the one who wielded it, the Dark Lord Sauron; they first appeared in this form in 2251 Second Age. What powers in battle or in sorcery they possessed we can only guess, but their main weapon was in the fear they inflicted in the hearts of men.
When Sauron went to Nśmenor as prisoner of Ar-Pharazōn, they hid, and led his forces again in the war of the Last Alliance. With Sauron defeated in that final battle, they passed into shadow, but were not destroyed as long as the Ring remained.
Around 1300TA, the Nazgūl reappeared, and the Lord of the Nazgūl founded a realm to the north of Middle-Earth, called Angmar, from which he invaded Arnor.
In many long struggles, the Nazgūl were eventually able to take the capital of the North Kingdom, Fornost, in 1974, but were driven back the succeeding year by troops led by the Elven Lord Glorfindel, whom even the Witch-King, Lord of the Nine, feared.
The Nazgūl withdrew, only to gather in the south, and take the city of Minas Ithil, gaining their master a palantķr, and themselves a place they soon turned into a city of dread as it became Minas Morgul, their dreadful base of operations.
In 2050, the Witch-King challenged the King of Gondor, Earnur, to a duel in exactly this place. He never reappeared, his honor preserved, but his life taken by the malice of the Ringwraiths.
When Sauron appeared again openly as the Necromancer of Dol Guldur, he soon became aware that the Ring was abroad, and he sent his Ringwraiths to find it. Some he had stay in southern Mirkwood, others in Minas Morgul, and when they learned from Gollum about Baggins and the Shire, and, later, from Grķma Wormtongue of the location of the Shire, they issued forth upon the lands of Middle-Earth in open terror as the Black Riders, shapeless spectres under black cloths, hunting the One Ring.
Only barely could the hobbits escape them in the Shire, since the Wraiths, even though bereft of human senses, afraid of fire and to cross bodies of water, could feel the presence of the Ring, especially when worn. In sunlight, they could only hardly fare abroad.
At Weathertop, five of the Nine almost achieved their goal, when they surrounded Frodo, only to be driven away by Aragorn, and the fire he wielded, but not before the Ringbearer was stabbed with a blade of black sorcery. Thusly injured, only the aid of Elrond and Gandalf, who commanded the river Bruinen, could save Frodo, when he was pursued by all assembled Nazgūl to the Ford in front of Rivendell. The incoming flood crushed the Wraiths, and forced them to flee to Mordor to regain their forms.
However, only a brief respite was granted to the Fellowship: soon they came upon Middle-Earth on flying steeds, patrolling the skies for the movements of the Free People. One Legolas shot with a well-aimed arrow, but the army of Morgul the Lord of the Nazgūl led forth upon the Pelennor was no less because of that. On the day of the great battle on the field of Pelennor, Théoden, King of Rohan, fell before the might of terror of the Lord of the Nazgūl, who in turn was slain by Éowyn and Meriadoc, and the prophesy Glorfindel once made that not by hand of man he would fall.
The Nazgūl met their final end no sooner than the destruction of the Ring achieved by the hobbits. When its power was undone, the Dark Tower collapsed and their Master vanished, they, too, perished into nothingness.
(See also: Witch-King, Minas Morgul, Angmar, One Ring, Sauron)
(References: LR, passim, I, 11; V, 6; Silmarillion, Of the Rings of Power and the Third Age; UT, III iv 1)