The Silmarillion

Upon Doriath a heavy change had fallen. Melian sat long in silence beside Thingol the King, and her thought passed back into the starlit years and to their first meeting among the nightingales of Nan Elmoth in ages past; and she knew that her parting from Thingol was the forerunner of a greater parting, and that the doom of Doriath was drawing nigh. For Melian was of the divine race of the Valar, and she was a Maia of great power and wisdom; but for love of Elwë Singollo she took upon herself the form of the Elder Children of Ilúvatar, and in that union she became bound by the chain and trammels of the flesh of Arda. In that form she bore to him Lúthien Tinúviel; and in that form she gained a power over the substance of Arda, and by the Girdle of Melian was Doriath defended through long ages from the evils without. But now Thingol lay dead, and his spirit had passed to the halls of Mandos; and with his death a change came also upon Melian. Thus it came to pass that her power was withdrawn in that time from the forests of Neldoreth and Region, and Esgalduin the enchanted river spoke with a different voice, and Doriath lay open to its enemies.

Thereafter Melian spoke to none save to Mablung only, bidding him take heed to the Silmaril, and to send word speedily to Beren and Lúthien in Ossiriand; and she vanished out of Middle-earth, and passed to the land of the Valar beyond the western sea, to muse upon her sorrows in the gardens of Lórien, whence she came, and this tale speaks of her no more.

Thus it was that the host of the Naugrim crossing over Aros passed unhindered into the woods of Doriath; and none withstood them, for they were many and fierce, and the captains of the Grey-elves were cast into doubt and despair, and went hither and thither purposeless. But the Dwarves held on their way, and passed over the great bridge, and entered into Menegroth; and there befell a thing most grievous among the sorrowful deeds of the Elder Days. For there was battle in the Thousand Caves, and many Elves and Dwarves were slain; and it has not been forgotten. But the Dwarves were victorious, and the halls of Thingol were ransacked and plundered. There fell Mablung of the Heavy Hand before the doors of the treasury wherein lay the Nauglamír; and the Silmaril was taken.

At that time Beren and Lúthien yet dwelt in Tol Galen, the Green Isle, in the River Adurant, southernmost of the streams that falling from Ered Lindon flowed down to join with Gelion; and their son Dior Eluchíl had to wife Nimloth, kinswoman of Celeborn, prince of Doriath, who was wedded to the Lady Galadriel. The sons of Dior and Nimloth were Eluréd and Elurín; and a daughter also was born to them, and she was named Elwing, which is Star-spray, for she was born on a night of stars, whose light glittered in the spray of the waterfall of Lanthir Lamath beside her father's house.

Now word went swiftly among the Elves of Ossiriand that a great host of Dwarves bearing gear of war had come down out of the mountains and passed over Gelion at the Ford of Stones. These tidings came soon to Beren and Lúthien; and in that time also a messenger came to them out of Doriath telling of what had befallen there. Then Beren arose and left Tol Galen, and summoning to him Dior his son they went north to the River Ascar; and with them went many of the Green-elves of Ossiriand.

Thus it came to .pass that when the Dwarves of Nogrod, returning from Menegroth with diminished host, came again to Sarn Athrad, they were assailed by unseen enemies; for as they climbed up Gelion's banks burdened with the spoils of Doriath, suddenly all the woods were filled with the sound of elven-horns, and shafts sped upon them from every side. There very many of the Dwarves were slain in the first onset; but some escaping from the ambush held together, and fled eastwards towards the mountains. And as they climbed the long slopes beneath Mount Dolmed there came forth the Shepherds of the Trees, and they drove the Dwarves into the shadowy woods of Ered Lindon: whence, it is said, came never one to climb the high passes that led to their homes.