Qalmë-Tàri. ( Mistress of Death )
Nienna is sister to Mandos and Lorien and she lives alone in her realm of shadow, where her throne is hidden. Her halls are West of West, near the borders of the world and the darkness, and her windows look outward from the Walls of the Night. Her gift is sorrow, and she knows of pain. She cries for all the wounds Melkor has caused to Arda. Yet Niënna is not crying for herself. Those who listen to her will learn the skills of compassion and hope. Niënna turns grief into wisdom and gives strength to the souls, and pity is her heart. It is said that even in the Music Niënna took little part, but listened intent to all that she heard. Therefore, she was rich in memory and farsighted, perceiving that the theme should unfold in the tale of Arda. But she had little mirth, and all her love was mingled with pity, grieving for the harms of the world and for the things failed of fulfilment. So great was her truth that it is said she could not endure to the end of the Music. Niënna seldom comes to Valmar, the city of the gods, where all are glad. She goes rather to visit her brother in his hall Vê. Nienna lived in The Halls of Mandos, which were far to the North away from the light of the Trees and the brilliance of Valmar. The Halls of Mandos were the abode of both Mandos and of Nienna, but they did not live together, for each had their own hall there. Niënna`s hall was named Fui. Nienna gathered in her hall the souls of the dead Humans and after their judgement she sent them down to her ship Mournië, which lies at Hanstovánen.
Valian Years ( V.Y.) 0 - 3450.
V.Y 0 - 1500. Uncounted years filled with labouring had gone by in the timeless ages before the Gods decended into the world in the year 0. But Melkor contested the overlordship of Manwë and strife was in the world. Manwë summoned help and among those who heard him was Tulkas who came to his aid. Before his angry face Melkor fled out into Eä.
1500 - 1900. Now the gods planned and schemed and ordered and for all the seeds Yavanna had planted, Aulë made two great lamps, Ormal and Illuin, to light the earth and these were set in 1900 upon Helkar and Ringil.
V.Y. 1900 - 3450. Now began the Spring of Arda. The Gods settled at Almaren and the world came to life. Threes and beasts swelled the earth. Melkor, however, saw it from the outside of the Wall of Things and grew hot with envy when he heard it from his spies ( Sauron the chiefest of them ) who were already among the Gods. Manwë had called for a great feast and while the Gods were afterwards resting, Melkor crept over the Wall and entered Arda in the North. He assailed the Lamps and overthrew them and the blossom of the earth was checked.
V.Y.3450 - V.Y.3500. The Gods departed to Aman, where Aulë deemed the plains of Valinor a good place to build their new home. A great labour now began for the Gods.
Now began the Valian Years of the Trees. ( V.Y.t ) and a new reckoning of time.
V.Y.t 0. When Valinor was fully wrought and the mansions of the Gods were established, Yavanna hallowed Ezellohar before the Western gate. She sat long upon the grass singing a song of the power of things that grow in the earth and with her was Niënna, who watered the mould with tears. Upon Ezellohar came forth two slender shoots. Under her song the saplings grew and became tall and fair. And there, in the V.Y.t 0, came the two trees Telperion and Laurelin into being. And in the delicious light upon Valinor, Aulë began many new tasks.
V.Y.t.1495. Melkor and Ungoliant assailed the two Trees and their life was spilled and consumed by Ungoliant but before all life was utterly gone Yavanna came to Ezellohar and laid hands on the trees and she perceived that some small life was still in the roots that could be saved with the light in the Silmarils if Fëanor would give them up but this he would not. Nienna then went to the hill and with her tears and song she washed away the defilement of Ungoliant.
Related links..: Battles: War of the shaping Arda. Misc.: Making of the Lamps. Encyc.: Niënna.