§ Of the Flight of the Noldor The Silmarillion

And thus the fear of Yavanna that the Silmarils would be swallowed up and fall into nothingness did not come to pass; but they remained in the power of Morgoth. And he being freed gathered again all his servants that 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 threefold peaks of Thangorodrim, and a great reek of dark smoke was ever wreathed about them. There countless became the hosts 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 on Beleriand, as is told hereafter, but in Angband Morgoth forged for himself a great crown of iron, and he called himself King of the World. In token of this he set the Silmarils in his crown. His hands were burned black by the touch of those hallowed jewels, and black they remained ever after; nor was he ever free from the pain of the burning, and the anger of the pain. That crown he never took from his head, though its 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 weapon, while his realm lasted.