Clara Lanfranc

Clara Orchid Frank (クララ・ランフランク, Kurara ranfuranku) is the temporary younger sister of Lelouch vi Britannia in Code Geass: Oz the Reflection, before she is killed by Orpheus Zevon and is eventually replaced by Rolo Lamperouge. While she acted as Lelouch's sister she went by the name Clara Lamperouge. She was given her Geass power from V.V. and is a member of the Geass Directorate.

Geass
Clara's Geass gives her the ability to make the body of another obey her commands regardless of their will by gazing at the person within her sight and calling out their name. This ability only works if she calls the target by their real name, which is why it had no effect on Orpheus while he was disguised as Oldrin with his Geass power.