The following article contains spoilers for The Lord of the Rings: The Rings of Power and Middle-Earth Legends.
The Lord of the Rings: The Rings of Power establishes Sauron as the major threat Middle-earth will face during the Second Age of Arda, the world created by J.R.R. Tolkien. Despite this, the series underscores how the world is still recovering from a catastrophic war against Morgoth, the Dark Enemy of all creation.
In the Beginning, There was Melkor
Eru, also known as Iluvatar, was the first thing Eru ever created were spirits who lived with him long before time even existed. Only one Ainur, Melkor, tries to play his own tune in disobedience. This first song would become a vision of a world filled with life, Arda, and even Melkor's dissonance.
The Ainur are enchanted by Arda, but Eru soon clarifies that their job will be to fulfill Arda, and that they will use their powers to create Arda, and they are known as the Valar. Melkor is also ashamed for being humiliated by Eru, and angry about the fact that God was creating the world for Elves and Men, and not for himself. Therefore, Melkor used his powers to bring to life dark creatures that are twisted versions of all good things in the lands.
Melkor is partly to blame for the existence of Balrogs, for example. They were followed by lesser Ainur who became known as Maiar, who transformed fire spirits into demons filled with rage. Even Sauron was a Maia who became seduced by Melkor's promises of power. So, basically, any evil creature that roams the world comes from Melkor, with very few exceptions. Morgoth is a Sindarin word that means Dark Enemy.
Morgoth Is Born
After Melkor destroyed the Valinor Trees and stole the Silmarils for himself, the Noldor Elves declared war on Morgoth and anyone who attempted to steal these precious stones, leading to the many battles that are known as the War of the Jewels. That's why the Ardas map has changed so much over the centuries.
Morgoth is captured and locked away in the Void, behind the Door of Night, but he is said to return someday, bringing the end times with him. During this final war, Morgoth will be murdered, and the world will be rebuilt in perfecter by Eru, without evil. Unfortunately, Middle-earth still has to deal with the long shadow cast by Morgoth, with his general Sauron taking the lead of a legion of monsters.
The first two episodes of The Lord of the Rings: The Rings of Power are now available on Prime Video. New episodes are available every Friday.