Japanese Voice: Asako Dodo
English Voice: Kari Wahlgren
Throughout the series, Marianne is believed to be dead. Eight years prior to the series' events, she was gunned down inside the Imperial Palace after she herself had lowered security. It isn't revealed until much later that she was shot by V.V and Lelouch spends much of the series trying to find out the identity of the killer.
However, Marianne was not truly killed. She possessed a Geass ability (granted by C.C before she left the Geass Order) that allowed her to transfer her consciousness into another body upon death. At the time, the only available body was Anya Alstreim, a girl who would later grow up to become a Knight of the Round. As far as anyone else was concerned, Marianne had been assassinated by insurgents, but she survived and was secretly aiding the emperor in seeking out the Thought Elevators around the world so that they could one day link them together in order to initiate the Ragnarok Connection.
Marianne reappears in her true body before her son Lelouch and Suzaku Kururugi in the episode "The Ragnarok Connection". It is then that she reveals the truth behind her assassination and her power to inhabit other bodies. She also admits to helping Charles with initiating the Ragnarok Connection which will apparently imprint the collective unconsciousness of humanity upon the conscious world and join all people, living and dead, into a single being, creating a world without lies and deceit. Lelouch was apalled by this notion, believing that such a state of being would be stagnant and unchanging. Realizing that his mother was just as cold and heartless as his father, Lelouch rejected their plan and their ideals and used his Geass to command the collective unconsciousness to destroy Ragnarok and his parents along with it. Marianne disintegrated along with Charles before Lelouch's eyes.