Morgoth Raised Three Volcanic Mountains
“Thangorodrim perpetually spewed forth a dark black smoke,
often erupting in great flowing vents of lava when Morgoth was at war.”
Thangorodrim was a grouping of three vast mountains that stood above the underground fortress of Angband. Made from slag spewed from Angband’s furnaces and shaped by the power of Morgoth, each was a smoldering peak of fire, that rose up out of the Iron Mountains. The tops of Thangorodrim were perpetually belching fire and smoke, and sometimes lava flowed down it’s sides. The three peaks of Thangorodrim functioned as furnaces for Morgoth’s great smithies deep in Angband.
The central peak was the tallest of the three and into it was carved the Great Gates of Angband, with a deep causeway leading into the mountain, which was lined on either side with ramparts topped with vast towers. Upon the northern side of Thangorodrim, away from the entrance into Angband were secret tunnels from which the hosts of Morgoth could issue forth to assail the forces of Elves and Men.
After Melkor and Ungoliant destroyed the Two Trees and fled back to Middle-earth, Ungoliant demanded payment seeking the treasure that Morgoth carried with him, including the three Silmarils! When Morgoth refused her, she set her webs against him and he cried out in a terrible voice, calling forth this servants hiding in the ruins of Angband. The balrogs came forth with their whips of fire cutting her webs and driving her off. Then Morgoth began the rebuilding of Angband…
And thus the fear of Yavanna the the Silmarils would be swallowed up and fall into nothingness did not come to pass; but they remained in the power of Morgoth. And being freed gathered again all his servants the he could find, and came to the ruins of Angband. There he delved anew his vast vaults and dungeons, and above their gates he reared the three fold peaks of Thangorodrim, and a great reek of dark smoke was ever wreathed about them.
There countless became the of his beasts and his demons, and the race of the Orcs, bred long before, grew and multiplied in the bowels of the earth. Dark now fell the shadow of Beleraind, as is told hereafter; but in Angband Morgoth forged for himself a great crown of iron, and he called King of the World. In token of this he set the Silmarils in his crown. His hands were burned black by the touch of these hallowed jewels, and black they remained ever after; nor was he ever free from the pain of burning, and the anger of the pain. That crown he never took from his head, though it’s weight became a deadly weariness. Never but once only did he depart for a while secretly from his domain in the North; seldom indeed did he leave the deep places of his fortress, but governed his armies from his northern throne. And once only also did he himself wield wepon, while his realm lasted.
From The Silmarillion in the chapter ‘Flight of the Noldor’
Thangorodrim and Angband were destroyed in the War of Wrath at the end of the First Age of Middle-earth when the dragon Ancalagon the Black fell in great battle.
Then seeing that his hosts were overthrown and his power dispersed, Morgoth quailed, and he dared not come forth himself. But loosed upon his foes the last desperate assault the he had prepared, and out of the pits of Angband there issued the winged dragons, that had not before been seen; so sudden and ruinous was the onset of that dreadful fleet the the host of Valar were driven back, for the coming of the dragons was with great thunder, and lightening, and a tempest of fire.
But Eärendil came, shining with white flame, and about Vingilot were gathered all the great birds of heaven and Thorondor was their captain, and there was battle in the air all the day and through a dark night of doubt. Before the rising of the sun Eärendil slew Ancalagon the Black, the mightiest of the dragon-host, and cast him from the sky; and he fell upon the towers of Thangorodrim, and they were broken in his ruin.
Then the Sun rose, and the host of the Valar prevailed, and well-nigh all the dragons were destroyed; and all the pits of Morgoth were broken and unroofed, and the might of the Valar descended into the deeps of the earth. There Morgoth stood at last at bay, and yet unvaliant. He fled into the deepest of his mines. and sued for peace and pardon; but his feet were hewn from under him and he was hurled upon his face. Then he was bound with the chain of Angainor which he had worn aforetime, and his iron crown they beat into a color for his neck, and his head was bowed upon his knees. And the two Silmarils which remained to Morgoth were taken from his crown and they shone unsullied beneath the sky; and Eönwë took them, and guarded them.
Thus an end was made of the power of Angband in the North, and the evil realm was brought to naught; and out of the the deep prisons a multitude of slaves came forth beyond all hope into the light of day, and the looked upon a world changed.
From The Silmarillion in the chapter ‘Of the Voyage of Eärendil’