Full name: Sauron
History:Sauron was one of the Maiar, or lower angels. He was a student of Aulë, but when Melkor, the first Dark Lord, turned to evil, Sauron was one of the Maiar to follow him. Sauron became the chief of Melkor's servants, and was entrusted with one of Melkor's fortresses, Angband. One of Sauron's most impressive feats during his service to Melkor was his capture of the Elvish watch-tower, Minas Tirith. He filled it with werewolves and turned it into Tol-in-Gaurhoth (Isle of Werewolves). Sauron was also responsible for deviously tricking human outlaw Gorlim into thinking his wife was still alive. Gorlim, thinking he could save his wife if he betrayed his fellow outlaws, told Sauron his full story, and, as a reward, joined his wife in death. Sauron captured Beren, Finrod, and their companions during the Quest for the Silmaril, stripping the group of their disguises. A werewolf ate all of the other companions, but when it came for Beren, Finrod grappled with it, destroying it and himself in the process. Lúthien journeyed to Tol-in-Gaurhoth to rescue her beloved Beren. She was accompanied by the faithful dog Huan. Huan killed all the werewolves and when Sauron turned himself into a wolf, Huan fought and vanquished him. Lúthien forced Sauron to surrender the tower, and he fled from the place in vampire-form.
After Melkor was defeated by the Valar, Sauron claimed to repent, but was too proud to suffer any retribution. He refused to go to Valinor to receive Manwë's judgement, and he went back to his evil ways, building the tower of Barad-dûr and fortifying Mordor. Sauron still had the treacherous gift of appearing in fair shapes, and in one of these shapes he visited the Elves remaining in Middle-earth. Many, such as Gil-galad and Elrond, distrusted him and he had the sense not to even try to win them over. Others, like Celebrimbor and the other Elven smiths, welcomed him and his teachings gladly. They learned much from each other about ring-making, but Sauron finally achieved his purpose and had the knowledge to craft his master ring: the One Ring. The instant Sauron put it on, the smiths were aware of it and hid their other Rings, but the damage was already done. Sauron gathered the Rings of Power besides the Elven Rings (those three were hidden from him): he gave nine to mortal kings, ensnaring them into becoming Nazgul. He gave seven to dwarves, but they were much harder to make into slaves.
Sauron hated Elves and Men of Middle-earth, but above all he hated the humans who lived on Numenor, an isle between Middle-earth and Valinor. When Ar-Pharazon, King of Numenor, learned of Sauron's hatred and power, he sailed to Middle-earth, vanquished Sauron without even a battle (Sauron saw that fighting was futile against the might of the Numenoreans), and took Sauron back to Numenor with the rest of the army. Sauron began to be treated as a counselor rather than a prisoner of war, and he started to turn the King against the Valar. He convinced Ar-Pharazon to stop worshipping Iluvatar and the Valar, and instead to worship a "more powerful" figure: Melkor. Numenor became a hideous mutation of what it had started as. Those loyal to the King and Sauron began practicing human sacrifice, always picking their victims from those who opposed them. Sauron lied to the King and told him that if he set foot on Valinor, he would became immortal. Death had been the greatest foe of the Numenoreans; they envied the Elves' gift of immortality. Even though the Valar had set a ban on the Numenoreans coming beyond a set distance west of Numenor, Ar-Pharazon thought this scheme to sail to the land of the Valar was wise, and assembled an enormous fleet. Sauron did not come with the army, but stayed in Numenor: he knew all too well what would happen, even if he did not know what extent the results would go to. Ar-Pharazon did set foot on Valinor, but not only did he not become immortal, but he was killed in a landslide that occured the instance he touched the ground. The rest of the fleet was engulfed as the sea split in two and swallowed the ships. The water covered all of Numenor; only a few Numenoreans, including Elendil, Isildur, and Anarion, escaped. Sauron, though, managed to escape as well. He was immortal, and even though in the flood he lost his ability to assume a fair shape, his spirit still glided back to Mordor and assumed a new shape: the great lidless Eye of Sauron.
Sauron planned to enslave the world, and would have succeeded but for Elendil, King of Men, and Gil-galad, King of the Elves. The two Kings formed an alliance of Elves and Men and that army journeyed to Mordor and laid siege to it for seven years. At last, after what had seemed like ages of fighting, Elendil and Isildur threw Sauron down. They themselves were killed; Gil-galad was consumed by the heat from Sauron's body. Isildur son of Elendil cut the Ring off Sauron's hand and had the chance to destroy both the Ring and Sauron forever, but the Ring's evil power was already at work: the Ring seemed fair and precious to Isildur, and refused to harm it. He paid for this decision with his life: as he and his army traveled from Mordor, they were assaulted by a party of Orcs and Isildur was shot. The Ring fell into the river, and Sauron's spirit lived on. Sauron hunted long for the Ring, which would give him dominion over the earth, but even with the two words extracted from Gollum ("Shire" and "Baggins"), he failed to recover it. His folly was believing that his enemies would attempt to overthrow him and set a new lord in his place. It never occurred to him that they would attempt to destroy it altogether. Even after losing his captain, the Witch-king of Angmar, Sauron's victory still seemed certain, but at the exact moment when Sauron's opponents were nearly conquered, Frodo Baggins fulfilled his quest and destroyed the Ring. Sauron's power was utterly destroyed, and even if his spirit still lives on, it is too weak to take shape or cause any harm.