Who is General Doppelganger from The Looking Glass Wars and what is their importance?

General Doppelganger is a general who works for Queen Genevieve. General Doppelganger has the ability to turn into more than one person, often morphing into Generals Doppel and Ganger. After Redd takes over the throne again, General Doppelganger organizers an army of rebels against her, calling themselves Alyssians for Princess Alyss. In the end, General Doppelganger is at Alyss's side when she battles Redd.