Melkor

Melkor was the most powerful of the Ainur, but turning to darkness, became Morgoth, source of all Evil in Middle-earth. He was the original Dark Lord before Sauron.

Once the greatest of Eru Ilúvatar's followers, the disaffected Melkor created discordance in the Ainulindalë ("Music of the Ainur"). He sought to set himself up as master of the world and a creator in his own right.

Melkor was not called "Morgoth Bauglir" until he destroyed the Two Trees of Valinor, murdered Finwë, the High King of the Noldor Elves, and stole the Silmarils, inciting the great War of the Jewels that dominated the First Age.

The darker name, Morgoth Bauglir, the "Black Foe of the World", was then bestowed by Fëanor, son of Finwë, and the Elves called him thereafter by that name alone.

The name Morgoth is Sindarin and means "Dark Enemy", "Black Foe", or "Black Foe of the World". Bauglir is also Sindarin, meaning "Tyrant" or "Oppressor". Fëanor actually named him in Quenya, Moriñgotto or Moriñgotho, and this was later translated into Sindarin as Morgoth.

From his stronghold of Angband in the north of Beleriand, Melkor terrorized Middle-earth and transformed or gathered to him many of the monstrous races that continued to threaten the Free Peoples in later ages -- Orcs, Trolls, Dragons, Balrogs, and others.

Morgoth was finally defeated in the War of Wrath, a cataclysmic battle with his fellow Valar that flooded Beleriand, altered the landscape of Middle-earth, and ended the First Age. The Dark Lord was then banished to the outer void, where he remains to this day. His lieutenant Sauron carried on his work, establishing himself as the second Dark Lord.

For more information, see the following link:

• Wikipedia: Morgoth