Rise of Sauron (500 S.A.) - The enemy Sauron made a long journey to his post as Dark Lord of Middle Earth.  He began as a Maiar of Aulë (the master craftsman who created the race of Dwarves).

 

"...the greatest was that spirit whom the Eldar called Sauron, or Gorthaur the Cruel.  In the beginning he was of the Maiar of Aulë, and he remained mighty in the lore of that people." ~The Silmarillion (Valaquenta)

 

In those days he was named Mairon (the Admirable), but Morgoth enticed him away from the service of Ilúvatar into joining him and he became known as Sauron (the Abhorred).

 

"Of old there was Sauron the Maia, whom the Sindar in Belriand named Gorthaur.  In the beginning of Arda Melkor seduced him to his allegiance, and he became the greatest and most trusted of the servants of the Enemy, and the most perilous, for he could assume many forms, and for long if he willed he could still appear noble and beautiful, so as to deceive all but the most wary." ~The Silmarillion (Of the Rings of Power and the Third Age)

 

When Morgoth was finally defeated by the Valar and cast into the infinite Void, there was at last peace in Middle Earth...for a time.  But Sauron escaped and began to plan his rise to power.  Finally, in the year 500 of the Second Age, his presence began to be felt.

 

"A new shadow arises in the East.  It is no tyranny of evil Men, as your son believes; but a servant of Morgoth is stirring, and evil things wake again.  Each year it gains in strength, for most men are ripe to its purpose.  Not far off is the day, I judge, when it will become too great for the Eldar unaided to withstand." ~Unfinished Tales (Aldarion and Erendis)