has he also been the necromancer?
Yes., in the south of Mirkwood.
Sauron
Sauron concealed himself in the south of Mirkwood as the Necromancer, in the stronghold of Dol Guldur, "Hill of Sorcery". T
who has a ring of power in lotr Sauron. who is he/she? The title character and the main antagonist of "The Lord of the Rings". is it a series or a novel? A novel in three volumes. who is the author of this novel? J. R. R. Tolkien. has it been adapted in any form? It  has been adapted for film, radio, stage, and television. which war was the main antagonist involved in? War of the Last Alliance. what was his role as a servant? He served Aulë the Vala Smith, acquiring much knowledge.
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Sauron [SEP] The Necromancer of Dol Guldur
Sauron concealed himself in the south of Mirkwood as the Necromancer, in the stronghold of Dol Guldur, "Hill of Sorcery". The Valar sent five Maiar as Wizards to oppose the darkness, supposing it was a Nazgûl rather than Sauron himself. The chief of the Nazgûl, the Witch-king of Angmar, repeatedly attacked the northern realm of Arnor, destroying it. When attacked by Gondor, the Witch-king retreated to Mordor, gathering the Nazgûl there. The Nazgûl captured Minas Ithil, which was renamed Minas Morgul, and seized its "palantír", one of the seven seeing stones brought from Númenor. Sméagol's friend Déagol found the One Ring in the River Anduin, Sméagol, later known as Gollum, killed Déagol to get it, and was swiftly corrupted by it.