Mouths of Sirion
The lands near the Mouths of Sirion were home to surviving Sindar of Doriath after that land was destroyed. Some Ñoldor from Nargothrond and Gondolin, as well as the few survivors of the Three Houses of the Edain, also settled near the Mouths of Sirion. The first rulers of this region, known as Arvernien, were Tuor of the Edain and Idril of Gondolin. Later their son Eärendil Half-elven, married the Half-elven Elwing, Dior's daughter and survivor of the Sack of Doriath. Elros and Elrond, the sons of Eärendil and Elwing, were born in Arvernien.
Elwing possessed the Silmaril of Beren and Lúthien. The refugees built many ships, sailing across the seas and to the nearby Isle of Balar where Círdan had fled with the survivors of Eglarest and Brithombar.
Eärendil built the ship Vingilótë and sailed far seeking the hidden land of Valinor to ask for the pardon of the Valar. But though his journeys carried him to many shores, Eärendil was unsuccessful. While he was at sea, the surviving Sons of Fëanor attacked the Mouths of Sirion to reclaim the Silmaril. They killed many people but were almost all slain themselves, save for Maedhros and Maglor. Elwing cast herself into the Sea with the Silmaril, but was saved by the Vala Ulmo and sent to Eärendil. Maglor later repented, and raised Elros and Elrond as his foster children.
With the power of the Silmaril, Eärendil and Elwing found a passage to Valinor, where he pleaded on behalf of Elves and Men with the Valar.
In one version of the Silmarillion mythology, the chief army of the Valar landed at the Mouths of Sirion during the War of Wrath. By the end of the War, most of the survivors of Beleriand gathered at the Mouths and the Isle of Balar, and many of them went to Lindon until the Elves were summoned to Valinor, and the Edain to the new isle of Númenor.