A/N:
This was inspired by a section in the Unfinished Tales about the Nazgul during the Hunt for the Ring in the Shire:
"...the Black Captain...himself visited the Barrow-downs. In notes on the movements of the Black Riders at that time it is said that the Black Captain stayed there for some days, and the Barrow-wights were roused, and all things of evil spirit, hostile to Elves and Men, were on the watch with malice in the Old Forest and on the Barrow-downs." Disclaimer:
Night lay thick and heavy over the ancient hills of the Barrow-downs, and pale pricks of starlight glimmered far overhead, cold and forlorn. A blanket of hazy white fog was swiftly spreading over the landscape of burial mounds, and soon the dark sky was blotted from view. Sight itself was made more difficult . The green turf was covered in droplets of dew underfoot.
A large standing stone reared up from the fog in this area, like a finger of the earth pointing straight into the night. The cry of a strange bird bounced from burial mound to stone. Then all was silent. Nothing stirred.
Clip. Clop. Clip. Clop.
Slowly but steadily, the faint but unmistakable sound of hoof clicking against rock could be heard, plodding along at an easy pace. The fog-shadows shifted, and from their midst a horseman trotted, covered from head to toe in a hooded black cloak. Upon his cowled head a metal crown gleamed, spiked and cruel. Onward the sable horse clopped, until it drew level beside the standing stone. There, the rider halted, and sat motionless. The hood was tilted as though listening. Minutes passed in wait.
But then, due to impatience or otherwise, the horseman straightened, and lifting high his head, he let forth a terrible shriek that careened through the murky air in notes of dread of despair. And another cry answered; this one low and menacing, and seemingly coming from the very ground itself. The earth groaned, and a yard or so from the standing stone there was the sound of many rocks tumbling. A second figure emerged from the fog, and stopped before the rider.
Unlike the first arrival, this late comer was not mounted, nor was its body concealed from view. Large pale eyes shone from a gaunt and skeletal face, and the creature was clothed in ancient and bloodied armor. Its hands were thin and its fingers were like bones. When it spoke its hollow voice was whispery and devoid of life.
"It has been long," said the Barrow-wight, "since you sent us here. You called, and we answered. Now you call anew, and again we answer."
"Tardy," acknowledged the horseman, though his cowl nodded in satisfaction, "but not overly so. My coming was unlooked for, afterall. Indeed I call upon your aid once more, as I did upon a time." The Ringwraith's horse snorted and stamped its feet; white streamed from its nostrils in the cold.
"I listen, lord," the Wight replied, inclining its skull-like head briefly, and fixing its dead unblinking stare on the robed shape. "What service may we offer? We have driven all Men from this place long ago, and few dare to enter these haunts."
"Some may yet dare," hissed the Witch-king, and as his hood turned, a faint crimson flicker betrayed the presence of two fiery eyes, "when other roads prove treacherous, and when they know not what hides in these hills. Rouse your brethren: be watchful, that is my bidding. Any wanderers that you find, you are to seize and retain until my return."
The Barrow-wight was silent for a moment, ere inquiring, "Retain…alive or slain?" There was the hint of eagerness in the tone, and the creature clasped its spidery fingers together.
A menacing rasp responded. "Unharmed." The Nazgûl raised a clenched glove into the night, and the shadows groped and wrapped round the second figure. The Wight drew itself down lower to the ground, and gave an odd moaning noise. "Any trinkets they posses, you are to place aside for my inspection. Hoard them for yourself, and I shall lay bare your mounds until you shrivel in the daylight."
"As you wish," said the Barrow-wight, clearly disappointed, and it did not meet the Wraith-lord's fiery eyes. Instead, it stooped back a series of paces, and vanished into the earth with another sound of shifting stones. "It shall be as you command," the final promise drifted up from the dirt beneath the black horse's hooves.
Long did the Ringwraith's gaze linger after the departed creature, ere at last his hood turned away; and with the shadows writhing and coiling about him, he steered his steed round and galloped back into the mists.