The tale of the Nauglafring is the last fully-written narrative in The Book of Lost Tales. The subsequent (and the all-important) Tale of Eärendel exists only in drafts and fragments. However, it is possible to get a glimpse of how this Tale would have turned out by quoting the relevant portion of Tolkien's "Sketch of the Mythology" which he wrote in 1926. The text has been slightly emended to bring it in accord with the earlier Tales, although some differences remain.
Sirion's mouth Elwing daughter of Dior dwelt, and received the
survivors of Gondolin. These become a seafaring folk, building many
boats and living far out on the delta, whither the Orcs dare not come.
reproaches the Valar, and bids them rescue the remnants of the Noldoli
and the Silmarils in which alone now lives the light of the old days of
bliss when the Trees were shining.
The sons of the Valar led by Fionwe Tulkas' son lead forth a host, in which all the Qendi march, but remembering Swanhaven few of the Solosimpi go with them. Kôr is deserted.
Tuor cannot forbear the call of the sea, and builds Earame and sails West with Idril and is heard of no more. Eärendel
weds Elwing. The call of the sea is born also in him. He builds
Wingelot and wishes to sail in search of his father. Here follow the
marvellous adventures of Wingelot in the seas and isles, and of how Eärendel slew Ungoliant in the South. He returned home and found the Waters of Sirion desolate. The sons of Fëanor
learning of the dwelling of Elwing and the Nauglafring had come down on
the people of Gondolin. In a battle all the sons of Fëanor
save Maidros and Maglor were slain, but the last folk of Gondolin
destroyed or forced to go away and join the people of Maidros. Maglor
sat and sang by the sea in repentance. Elwing cast the Nauglafring into
the sea and leapt after it, but was changed into a white sea-bird by
Ulmo, and flew to seek Eärendel, seeking about all the shores of the world.
son (Elrond) who is part mortal and part elfin and part of the race of
Valar, a child, was saved however by Maidros. When later the Elves
return to the West, bound by his mortal half he elects to stay on earth.
Through him the blood of Huor and of Beren (his great-grandfather) and
of the Elves is yet among Men, and is seen yet in valour and in beauty
and in poetry.
learning of these things from Bronweg, who dwelt in a hut, a solitary,
at the mouth of Sirion, is overcome with sorrow. With Bronweg he sets
sail in Wingelot once more in search of Elwing and of Valinor.
He comes to the magic isles, and to the Lonely Isle, and at last to the Bay of Faerie. He climbs the hill of Kôr, and walks in the deserted ways of the city, and his raiment becomes encrusted with the dust of diamonds and of jewels.
dares not go further into Valinor. He builds a tower on an isle in the
northern seas, to which all the seabirds of the world repair. He sails
by the aid of their wings even over the airs in search of Elwing, but is
scorched by the Sun, and hunted from the sky by the Moon, and for a
long while he wanders the sky as a fugitive star.