Sauron

Sauron, also know as The Necromancer, is a prominent antagonist in J.R.R Tolkien's Middle-earth novels, specifically The Hobbit and Lord of the Rings.

Past
Sauron was originally a powerful Maiar (an angel-esque entity) labeled Mairon who worshiped Melkor, a barbaric dark lord, and became the high general of Angband. When assigned the task to corrupt elves into brutish orcs, Sauron watched as the Valar marched their way into Middle-earth, sick of its evil layout, and defeated Melkor. Such an action triggered the War of the Jewels, which Sauron played a large part in as he used his werewolf/vampire servants and mastery of illusions to lead himself to victory. After Melkor, later called Morgoth, went to go corrupt the newly discovered man species, Sauron shifted the war towards the elves. However, wolfhound Huan and elven maiden Luthien stepped their way into the war in hopes of saving a recently captured human named Beren. The two warriors thwarted Sauron after he attempted to defeat them by transforming into a wolf-like creature and had him by his throat. Luthien gave Sauron two options: surrender the control of Tol-in-Gaurhoth, a captured island, over to her or have his body destroyed and sustain Morgoth's lecturing. Sauron of course picked the former and was let go. Ultimately, Morgoth was banished to the void and Sauron returned to his realm, Mordor.

Second Age
Still ruling Mordor 500 years into the Second Age, Sauron was reincarnated into the embodiment of pure evil, lusting for complete power. Sauron then, in an attempt to seduce the elves to his side, assumed the appearance of Annatar, the Lord of Gifts, and befriended them. Hinting that he was the emissary of the Valar, Sauron and the elves constructed the Rings of Power, which reflected great power upon the wearers. However, secretly, Sauron formed the One Ring in Mount Doom, a volcano in Mordor, and sculpted it so it can mentally enslave the other ring bearers, labeling it the "One ring to rule them all". Despite this, the elves saw through Sauron's master plan and refused to don the rings as long as he had the One Ring, enraging the dark lord enough for him to officially wage war on them. At the end of the war, Sauron nearly won until the Númenoreons arrived to thwart his tyranny and drive him back to Mordor yet again. Sauron later gave the nine rings to the dwarves and men, the dwarves being too smart for Sauron's tricks, but the men were not. Sauron then used the One Ring to turn the men into his ghostly slaves called the Nazgul. The dark lord also began constructing his army by taking in orcs and trolls from Morgoth's original ranks.