This from Terez's database (https://docs.google.com/View?docID=dcjspjqg_88d7dvmtc4&revision=_latest)

Week 12 Question: In Winters Heart, you mention that back in the Age of Legends, there were several other Forsaken that the Dark One had killed because he suspected they would betray him. What's their story? Were those people ever as high ranking as the thirteen survivors, or where they more like high-ranking Dreadlords then actual Forsaken?

Robert Jordan Answers: First off, Dreadlords was the name given to men and women who could channel and sided with the Shadow in the Trolloc Wars. Yes, the women were called Dreadlords, too. They might have liked to call themselves "the Chosen," like the Forsaken, but feared to. The real Forsaken might not have appreciated it when they returned, as prophecies of the Shadow foretold would happen. Some of the Dreadlords had authority and responsibility equivalent to that of the Forsaken in the War of the Shadow, however. They ran the Shadow's side of the Trolloc Wars, though without the inherent ability to command the Myrddraal that the Forsaken possess, meaning they had to negotiate with them. Overall command at the beginning was in another's hands.