Black King

One of the many names and titles used for Morgoth, the Dark Power who dwelt in the North of the world during the First Age, and warred against Elves and Men. He had escaped into Middle-earth after his long imprisonment in the Halls of Mandos, having stolen away the Silmarils and Darkened the Two Trees of Valinor. In Middle-earth he established himself in the fortress of Angband, where he sat on his Dark Throne wearing an Iron Crown that gleamed with the light of the stolen Silmarils.

The Noldor pursued the Black King into Middle-earth, and the Wars of Beleriand that followed would last for centuries. At first, the Elves appeared to have the upper hand, defeating Morgoth's Orcs in battle and setting up the Siege of Angband around the Black King's northern fortress. In later times, the tides of war began to turn to Morgoth's favour: he swept away the Siege in the Dagor Bragollach, and in the immense battle of the Nirnaeth Arnoediad he defeated the combined forces of Elves and Men. From the time of the Nirnaeth, the Black King's power continued to grow until he had destroyed most of his enemies and come close to ultimate victory.

No power remained in Middle-earth that could hope to challenge the Black King, but the Valar still dwelt beyond the Great Sea. Eärendil the Mariner made the perilous journey across that Sea to call on their aid, and they answered the call. The armies of the Valar went to war against the Black King, and the resulting War of Wrath lasted for decades, but ended in absolute defeat for Morgoth.

The names 'Black King' or 'Dark King' seem to have been most widely used among the Men of Beleriand. At least, all our recorded uses of these forms of title come from Men. In the particular form 'Black King' the title was used by Sador, the serving-man of Húrin (who had fought against Morgoth's armies himself in his youth). It therefore seems to have been an informal description rather than any kind of formal title.