Mao (Nightmare of Nunnally)

Mao is a character that only appear in Nightmare of Nunnally. She has a Geass ability granted by an infusion of cell matter from C.C. A Geass sigil lights up in her left eye when she uses it. Her Geass ability is known as "The Refrain," which allows her to read and manipulate the minds of others through eye contact.

Personality
Prior to her betrayal of the Irregular Mao is sick with how the Irregular treat her and her fellow teammates and as a result she betrayed the Irregular and escaped to Saitama Ghetto where she's now offer her service to the people living in the Ghetto by using her Geass to let them relive past experience, she described her acts as "helping" the people who were miserable but at the same time contradict herself by saying that pain is necessary to continue living and that she receive strength from it revealing a more complex person behind her

Character History
Mao is mentioned by Alice that she used to be an Irregulars member just like her, before she left she took a large amount of Neutralizer with her. She first appear in chapter 11 in Nightmare of Nunnaly trying to remove Nemo from Nunnally. Because C.C.'s cell matter causes cellular breakdown, she seeks to steal Nunnally's bond with Nemo, which she believes to be a possible cure. After Alice breaks Mao's remaining suppressants, before she died Mao curses Alice letting her know that this is the fate of all Artificial Geass User, then her body turn to dust and finally died.

Geass
Her Geass the Refrain in addition that it allow her to read the mind of other people and control it, it allows her to render her victim catatonic by forcing them to relive past experiences, similar to the drug in the anime it is named after. As an Artificial Geass User just like the rest of the Irregulars she also receive the same weakness as the rest of them, the C.C. Cell inside her will eventually reject her body causing the host to died from the process.

Knightmare
In one Panel Mao Seems to had have a Sutherland as Knightmare Frame, it is possible that the GX 01 Series is still not introduced to the Irregulars before she left.