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.