Hi, there is an mistake because betweendwarves and Necromancer, hill was used by silvans lead by Oropher
Dol Guldur was built on the hill known as Amon Lanc (meaning "bald hill"), and had been the capital of Oropher's Silvan realm. The Silvan Elves had fled north to the Black Mountains (later the Mountains of Mirkwood) after Sauron's return from the Downfall of Númenor. Later, after Sauron captured Amon Lanc, Thranduil, son of Oropher, led his people over the Forest River, where they remained. Sauron later remained there for hundreds of years.