The Silmarillion

But even in the hour of the death of Fëanor an embassy came to his sons from Morgoth, acknowledging defeat, and offering terms, even to the surrender of a Silmaril. Then Maedhros the tall, the eldest son, persuaded his brothers to feign to treat with Morgoth, and to meet his emissaries at the place appointed; but the Noldor had as little thought of faith as had he. Wherefore each embassy came with greater force than was agreed; but Morgoth sent the more, and there were Balrogs. Maedhros was ambushed, and all his company were slain; but he himself was taken alive by the command of Morgoth, and brought to Angband.

Then the brothers of Maedhros drew back, and fortified a great camp in Hithlum; but Morgoth held Maedhros as hostage, and sent word that he would not release him unless the Noldor would forsake their war, returning into the West, or else departing far from Beleriand into the South of the world. But the sons of Fëanor knew that Morgoth would betray them, and would not release Maedhros, whatsoever they might do; and they were constrained also by their oath, and might not for any cause forsake the war against their Enemy. Therefore Morgoth took Maedhros and hung him from the face of a precipice upon Thangorodrim, and he was caught to the rock by the wrist of his right hand in a band of steel.

Now rumour came to the camp in Hithlum of the march of Fingolfin and those that followed him, who had crossed the Grinding Ice; and all the world lay then in wonder at the coming of the Moon. But as the host of Fingolfin marched into Mithrim the Sun rose flaming in the West; and Fingolfin unfurled his blue and silver banners, and blew his horns, and flowers sprang beneath his marching feet, and the ages of the stars were ended. At the uprising of the great light the servants of Morgoth fled into Angband, and Fingolfin passed unopposed through the fastness of Dor Daedeloth while his foes hid beneath the earth. Then the Elves smote upon the gates of Angband, and the challenge of their trumpets shook the towers of Thangorodrim; and Maedhros heard them amid his torment and cried aloud, but his voice was lost in the echoes of the stone.

But Fingolfin, being of other temper than Fëanor, and wary of the wiles of Morgoth, withdrew from Dor Daedeloth and turned back towards Mithrim, for he had heard tidings that there he should find the sons of Fëanor, and he desired also to have the shield of the Mountains of Shadow while his people rested and grew strong; for he had seen the strength of Angband, and thought not that it would fall to the sound of trumpets only. Therefore coming at length to Hithlum he made his first camp and dwelling by the northern shores of Lake Mithrim. No love was there in the hearts of those that followed Fingolfin for the House of Fëanor, for the agony of those that endured the crossing of the Ice had been great, and Fingolfin held the sons the accomplices of their father. Then there was peril of strife between the hosts; but grievous as were their losses upon the road, the people of Fingolfin and of Finrod son of Finarfin were still more numerous than the followers of Fëanor, and these now withdrew before them, and removed their dwelling to the southern shore; and the lake lay between them. Many of Fëanor's people indeed repented of the burning at Losgar, and were filled with amazement at the valour that had brought the friends whom they had abandoned over the Ice of the North; and they would have welcomed them, but they dared not, for shame.

Thus because of the curse that lay upon them the Noldor achieved nothing, while Morgoth hesitated, and the dread of light was new and strong upon the Orcs. But Morgoth arose from thought, and seeing the division of his foes he laughed. In the pits of Angband he caused vast smokes and vapours to be made, and they came forth from the reeking tops of the Iron Mountains, and afar off they could be seen in Mithrim, staining the bright airs in the first mornings of the world. A wind came out of the east, and bore them over Hithlum, darkening the new Sun; and they fell, and coiled about the fields and hollows, and lay upon the waters of Mithrim, drear and poisonous.