In his creation Sauron was Ainur, a Maiar of the people of
Aule. he was regarded as mighty among that people until he lent ear to
the foul wisdom of Melkor. Thus Sauron fell from the light of the Valar
upon himself the yoke of Darkness, and he bowed to Melkor and called
Under the service of Melkor, Sauron's power grew great becoming a mastery of sorcery clothed in a shadow of fear. He rose to become Lieutenant of Melkor, and was given command of Angband while Utumno lasted. In Angband Sauron wrought shadows and dark phantoms and he bred the fell race of werewolves for his lord.
In the early days of the world, the Valar made war on Melkor and his servants. Utumno was broken and Melkor was captured and was put into the Halls of Mandos for three ages. Sauron was not found for he hid himself in the cracks of the earth. Secretly he prepared Angband for the return of his lord. Melkor did return and Sauron was again his lieutenant and Angband was built anew. Sauron would later again rule the forces of Angband in Melkor's stead, as his lord went in secret to seduce the secondborn in the hour of thier awakening.
Towards the middle part of the First Age, Sauron played a pivotal role in Melkor's plans of the conquest of Middle Earth. Sauron would become entangled in the 'dooms' of those days (as did many), most notably the oath of Finrod Felagund to Barahir and his kin, the doom of Huan hound of Valinor, and the fate of Beren and Luthien. Those were the years of 'The War of Sudden Flame' and the years that followed shortly after. In that war most of the kingdoms of elves and men were broken, but Minas Tirith the Tower upon Tol-Sirion held fast.
Sauron it was whom Melkor sent against that Tower. Sauron came at them with force and put forth his 'shadow of fear' and the defenders of Minas Tirith fled before his menace. From Tol-Sirion, later called Tol-in-Gaurhoth the isle of werewolves, Sauron spread fear into the lands of Dorthonion and the wilderness of Dungortheb.
The Sindar of those days named Sauron, Gorthaur the Cruel or Thu the Hunter, for in Dorthonion and in Dungortheb Sauron sent forth werewolves to cleanse the land in Melkor's name. Sauron made those places a domain of evil which stood in the face of Doriath and the protection of Melian the Maia. It is told that none could enter these lands that Sauron did not espy from his Tower in Tol-in-Gaurhoth.
As is told before Sauron was named Gorthaur the Cruel and Thu the Hunter by the Sindar and he earned those names in that he would hunt down the enemies of Melkor and with cruel torture learn their places of hiding. In this manner the hiding place of Barahir was laid bare and Sauron fulfilled Melkor's order to slay Barahir of Dorthonion. Sauron did not find Beren son of Barahir and a price was set on the head of Beren and Sauron was commanded to find him.
Upon a time Sauron did capture Beren though he knew not who he was at the time. Beren was at that time travelling with Finrod Felagund who had left his own kingdom to fulfill his oath to Barahir and his kin. Felagund with his power made Beren, himself and their companions disguises in the likeness of orcs. But Sauron in his Tower espied them and doubted them as they passed swiftly through Taur-nu-Fuin. Sauron and Felagund strove together in a song of power, but Sauron won the duel and cast away their disguises and learned their race, but not their names or their mission.
Sauron put his captives into the pits of his Tower and promised them death unless they give their names and errand. Sauron slew all of the companions of Beren and Felagund with cruel jaws of his wolves, but saved Felagund for last. But as Sauron's wolf came to take the life of Beren, Felagund burst his own bonds and slew the wolf yet died also, but by this he spared Beren. Sauron knew it not but he had helped Felagund fulfill his oath to Barahir and he knew not that the wisest and fairest of the Noldor had died in his pits.
Luthien, the love of Beren, came to Tol-in-Gaurhoth to rescue Beren, and with her came Huan, the hound of Valinor. Sauron the lord of werewolves knew well the doom of Huan, for he had lost many a wolf to the jaws of Huan, and he knew that the capture of Luthien would bring him great reward from Melkor, so Sauron put forth his power and made himself into the greatest wolf that ever walked and he came forth from Tol-in-Gaurhoth to fulfill Haun's doom and to capture Luthien.
Even as powerful as Sauron was, he could not complete the doom of Huan nor could he hinder the fate of Beren and Luthien and keep them apart. So it was that Huan defeated Wolf-Sauron and he surrendered the Tower of Tol-in-Gaurhoth to Luthien, but Sauron was not utterly vanquished.
Sauron fled to Tar-nu-Fuin and built a new fortress and he filled that land with evil. For the remainder of the First Age Sauron would serve his lord in all his deeds until the Valar came and ended the reign of Angband.