Nienor was the third child of Húrin Thalion, Lord of House of Hador, and Morwen Eledhwen of the House of Bëor. Her elder brother was Túrin, but her sister Lalaith died of a plague four years before Nienor’s birth. Nienor “was tall, and her eyes were blue, her hair fine gold, the very likeness in woman’s form of Húrin her father.”
Swiftly she came to the brink of Cabed-en-Aras, and there stood and looked on the loud water crying: ‘Water, water! Take now Níniel Nienor daughter of Húrin; Mourning, Mourning daughter of Morwen! Take me and bear me down to the Sea!’ With that she cast herself over the brink: a flash of white swallowed in the dark chasm, a cry lost in the roaring of the river.
'Thus ended Beleg Strongbow, truest of friends, greatest in skull of all that harboured in the woods of Beleriand in the Elder Days, at the hand of he whom he most loved; and that grief was graven on the face of Túrin and never faded.' - Of Túrin Turambar, The Silmarillion.