Part 4/10:
During the events of The Hobbit, Sauron had already regained physical form. He chose to operate from the shadows, adopting the guise of a human necromancer residing in the ruins of Dol Guldur. Tolkien acknowledged that Sauron was immortal and managed to escape the destruction of Númenor to regain strength in Mordor. By the time the Second Age concluded with the Last Alliance of Elves and Men, Sauron's visible incarnation of evil was once again eradicated, but his spirit fled into obscurity.