§ Of the Sindar The Silmarillion

But it came to pass at last that the end of bliss was at hand, and the noontide of Valinor was drawing to its twilight. For as has been told and as is known to all, being written in lore and sung in many songs, Melkor slew the Trees of the Valar with the aid of Ungoliant, and escaped, and came back to Middle-earth. Far to the north befell the strife of Morgoth and Ungoliant; but the great cry of Morgoth echoed through Beleriand, and all its people shrank for fear; for though they knew not what it foreboded, they heard then the herald of death. Soon afterwards Ungoliant fled from the north and came into the realm of King Thingol, and a terror of darkness was about her; but by the power of Melian she was stayed, and entered not into Neldoreth, but abode long time under the shadow of the precipices in which Dorthonion fell southward. And they became known as Ered Gorgoroth, the Mountains of Terror, and none dared go thither, or pass nigh them; there life and light were strangled, and there all waters were poisoned. But Morgoth, as has before been told, returned to Angband, and built it anew, and above its doors he reared the reeking towers of Thangorodrim; and the gates of Morgoth were but one hundred and fifty leagues distant from the bridge of Menegroth: far and yet all too near.