The Silmarillion

In that battle by Sarn Athrad Beren fought his last fight, and himself slew the Lord of Nogrod, and wrested from him the Necklace of the Dwarves; but he dying laid his curse upon all the treasure. Then Beren gazed in wonder on the selfsame jewel of Fëanor that he had cut from Morgoth's iron crown, now shining set amid gold and gems by the cunning of the Dwarves; and he washed it clean of blood in the waters of the river. And when all was finished the treasure of Doriath was drowned in the River Ascar, and from that time the river was named anew, Rathlóriel, the Goldenbed; but Beren took the Nauglamír and returned to Tol Galen. Little did it ease the grief of Lúthien to learn that the Lord of Nogrod was slain and many Dwarves beside; but it is said and sung that Lúthien wearing that necklace and that immortal jewel was the vision of greatest beauty and glory that has ever been outside the realm of Valinor; and for a little while the Land of the Dead that Live became like a vision of the land of the Valar, and no place has been since so fair, so fruitful, or so filled with light.

Now Dior Thingol's heir bade farewell to Beren and Lúthien, and departing from Lanthir Lamath with Nimloth his wife he came to Menegroth, and abode there; and with them went their young sons Eluréd and Elurín, and Elwing their daughter. Then the Sindar received them with joy, and they arose from the darkness of their grief for fallen kin and King and for the departure of Melian; and Dior Eluchíl set himself to raise anew the glory of the kingdom of Doriath.

There came a night of autumn, and when it grew late, one came and smote upon the doors of Menegroth, demanding admittance to the King. He was a lord of the Green-elves hastening from Ossiriand, and the door-wards brought him to where Dior sat alone in his chamber; and there in silence he gave to the King a coffer, and took his leave. But in that coffer lay the Necklace of the Dwarves, wherein was set the Silmaril; and Dior looking upon it knew it for a sign that Beren Erchamion and Lúthien Tinúviel had died indeed, and gone where go the race of Men to a fate beyond the world.

Long did Dior gaze upon the Silmaril, which his father and mother had brought beyond hope out of the terror of Morgoth; and his grief was great that death had come upon them so soon. But the wise have said that the Silmaril hastened their end; for the flame of the beauty of Lúthien as she wore it was too bright for mortal lands.

Then Dior arose, and about his neck he clasped the Nauglamír; and now he appeared as the fairest of all the children of the world, of threefold race: of the Edain, and of the Eldar, and of the Maiar of the Blessed Realm.

But now the rumour ran among the scattered Elves of Beleriand that Dior Thingol's heir wore the Nauglamír, and they said: 'A Silmaril of Fëanor burns again in the woods of Doriath'; and the oath of the sons of Fëanor was waked again from sleep. For while Lúthien wore the Necklace of the Dwarves no Elf would dare to assail her; but now hearing of the renewal of Doriath and of Dior's pride the seven gathered again from wandering, and they sent to him to claim their own.

But Dior returned no answer to the sons of Fëanor; and Celegorm stirred up his brothers to prepare an assault upon Doriath. They came at unawares in the middle of winter, and fought with Dior in the Thousand Caves; and so befell the second slaying of Elf by Elf. There fell Celegorm by Dior's hand, and there fell Curufin, and dark Caranthir; but Dior was slain also, and Nimloth his wife, and the cruel servants of Celegorm seized his young sons and left them to starve in the forest. Of this Maedhros indeed repented, and sought for them long in the woods of Doriath; but his search was unavailing, and of the fate of Eluréd and Elurín no tale tells.

Thus Doriath was destroyed, and never rose again.

But the sons of Fëanor gained not what they sought; for a remnant of the people fled before them, and with them was Elwing Dior's daughter, and they escaped, and bearing with them the Silmaril they came in time to the mouths of the River Sirion by the sea.

Chapter 23 Of Tuor and the Fall of Gondolin