the Necromancer

[Boromir88]

Saruman for one knew the Necromancer was Sauron. He discovered his servants searching near the Gladden fields, for the "one ring." At this time the One ring had been in Bilbo's posession, but no one knew that. When Saruman discovered this he did not tell the White Council, Saruman being head of the White Council knew but he didn't warn any of the others. Of course later on Galadriel and Saruman drove out the Necromancer.