For many years Gandalf wandered among the Free Men of Middle-earth, but spent most of his time among the Elves, where he learned much and taught much. He also continued to gather as much information as he could about Sauron and his kind, and eventually began to suspect that the Necromancer in Dol Guldur was indeed Sauron’s reincarnation.
Dol entered Guldur but Sauron was still greatly weakened, fleeing from him, and for a short time Mirkwood’s evil was greatly diminished.
However, Sauron quickly returned to Dol Guldur and rebuilt his forces there by 2850 of the Third Age.
That year, Gandalf again entered the castle and encountered Thráin II, the father of Thorin Oakenshield, who died after being horribly tortured. Before his death, the old dwarf king gave Gandalf a map and the key to the Lonely Mountain.
