“Morgoth, the first Dark Lord of Middle-earth.”— Talion
The great rebel Vala and a primordial source for the evil that festers in Middle-earth, Morgoth defied the creator of Arda when all was at its beginning and sowed discord among the Ainur. He then became one of the main adversaries of the Powers and the Elves as the first Dark Lord, toiling to mar and ultimately unmake Middle-earth by open war. Eventually, he was defeated by the Powers and cast beyond the Walls of Arda, leaving his former lieutenant Sauron to trouble the Free Peoples in future ages.
Originally, Morgoth had been the mightiest among the Ainur in terms of raw strength, being surpassed only by his brother Manwë in wisdom and understanding of Ilúvatar's designs. Failing to learn to master the Flame Imperishable for his own ends, Morgoth rebelled against his creator, spreading dissent wherever he went and compelling others to willfully do his bidding.
After his coming to Middle-earth he began waging a conflict to defeat the other Valar, while he attempted to twist Arda to his own foul image and ultimately destroy its very matter. Though he was defeated and captured, Morgoth did not repent of his misdeeds and his nihilistic hatred only increased by the time he returned to Middle-earth.
The spawner of many evil things that still plague Middle-earth, such as the foul black-blooded race of Orcs or the fiery demons that are the Balrogs, Morgoth amassed immeasurable armies with which he warred with the Elves and their allies, crippling one kingdom after another and leaving only destruction in his wake. By the time of the last Wars of the First Age, victory seemed all but certain for the Dark Lord for the Elves were scattered and many Men either enslaved or fled. And he would have been triumphant, had the Host of the West not come upon him and he could not prevail against the might that was arrayed against him.
Defeated by the Powers, Morgoth was thrown through the Door of Night into the chaotic nothingness since before Arda was made. However, his former great servant Sauron rose to follow the same path as a foe to the Free Peoples and the Powers, while those Men seduced by their lies would deify them and worship the Darkness. According to a prophecy of Mandos, Morgoth will return at the very End for the Last Battle.
In the "Shadow of " Series
Morgoth himself does not appears and is only fleetingly mentioned throughout the series, but some of his legacy is crucial to the plots of Sauron and his servant Zog, who plan to build an undead army to reclaim all of Mordor and defeat the Bright Lord.
At Sauron's command, Zog and his Acolytes wake the rampaging Balrog Tar Goroth and later resurrect the Archers of Morgoth - an elite division of the first Dark Lord's marksmen. Both are foiled by the combined might of Talion, Celebrimbor and the spirit of Carnán. Furthermore, the Ghûl-infested cave in Núrn is called Morgoth's Scar, in refference to the elder Vala, while a graven idol of him, carried to the mainland by his worshippers is found in Udûn.
In Blade of Galadriel, it is revealed that at least one of Morgoth's elite archers is still alive: Ogg, an orc marksman from a bygone age. He looks down on those loyal to Sauron, regarding him as a base impostor of the first (and for him only) Dark Lord. Ogg's disdain for "the Usurper" is strong enough for him to willingly forge an alliance with the elven assassin Eltariel, despite Morgoth's deep hatred for the elven folk.