Elwing was the daughter of Dior, Thingol's heir, and of Nimloth, and so the granddaughter of Beren and Lúthien. She was in Doriath when the sons of Fëanor destroyed it for the sake of the Silmaril, which Dior had inherited from his parents and wore in the Nauglamír, the necklace of the Dwarves.1
Elwing escaped from the ruin with the Silmaril, with a few of Dior's people, and came to the mouths of the river Sirion, where Círdan the Shipwright's people, with the survivors of Gondolin and Doriath, had made their havens. There she wed Eärendil, who came from Gondolin, and bore him two sons, Elrond and Elros.1,2
The sons of Fëanor, who had sworn to have the Silmaril back, attacked the Havens and destroyed them. Elwing, rather than yield it, threw herself into the sea with the jewel. Ulmo bore her up and turned her into a white sea-bird, and she flew over the waves to find Eärendil on his ship, and came to him with the Silmaril shining on her breast.2
With the Silmaril on his brow, Eärendil was able to find his way to Valinor, to plead for Elves and Men. When the two came before the Valar, Manwë gave each the choice of kindred. Elwing chose to be judged among the Elves, for the sake of Lúthien, and Eärendil, whose heart was drawn to Men, chose the same for her sake.2
Sources
Citations name the chapter rather than the page, so they work in any edition. The colour of each note shows what kind of source it is.
- Edited posthumously The Silmarillion, Unfinished Tales and Tolkien's late writings on the Elder Days, assembled by Christopher Tolkien from his father's papers.
- Edited posthumously The Silmarillion, Quenta Silmarillion, ch. 22, “Of the Ruin of Doriath”
- Edited posthumously The Silmarillion, Quenta Silmarillion, ch. 24, “Of the Voyage of Eärendil and the War of Wrath”