Sauron

Originally one of the Maiar—immortal lesser divine spirits created before the shaping of the world—Sauron served the Vala Aulë before being drawn into rebellion and serving Morgoth (Melkor) as his chief lieutenant. After Morgoth's defeat, Sauron persisted in Middle‑earth, pursuing a project of domination that culminated in the forging of the One Ring during the Second Age and centuries of warfare and subversion thereafter.

Sauron's appearances vary across the legendarium: he once assumed a fair guise as Annatar, 'Lord of Gifts', to seduce Elven smiths; in the First Age he is described assuming terrible animalistic shapes (e.g., werewolf or huge vampire bat) in combat; after the loss of the One Ring he spent a long period as a shapeless evil. In later narrative emphasis he is frequently represented symbolically as a disembodied 'Eye'. The sources note later reembodiment as the Necromancer at Dol Guldur and his later corporeal manifestation as the Dark Lord in Mordor.

Sauron is skilled in smithcraft and lore (having served Aulë) and used such knowledge to teach and deceive—most notably as Annatar when he taught Celebrimbor's Elven‑smiths. He secretly forged the One Ring to rule other Rings of Power and used Rings and gifts to bind and corrupt leaders (including the nine Rings given to Men that produced the Nazgûl). He marshalled armies (orcs, trolls, Easterlings, men of Harad), made war upon Elves and Men, and engaged in political and spiritual subversion (corrupting Númenor). He endured bodily destruction and persisted as a formless malign presence, later reembodying; his power is closely tied to the One Ring, whose loss or destruction greatly weakens him. The sources also record direct martial potency (killing Elendil and Gil‑galad in battle) and that he captured and tortured Gollum to learn of the Ring's whereabouts.