The Grandmaster (盟主(グランドマスター)) is the absolute leader of Ouroboros. The identity of the Grandmaster is unknown, but because the voice actor of the Ouroboros Report drama CD was female, it is believed that the Grandmaster is female.


During one scene in Trails in the Sky the 3rdCampanella reports the outcome of the Gospel Plan to Grandmaster in the Celestial Globe. Unlike the Anguis, she laments the passing of Anguis No. 3, Georg Weissmann, during the Gospel Plan. She also laments the sacrifice of Enforcer No. II, Leonhardt, whom she had given his demon sword Kernviter through forging with Divergent Laws, and demonstrates a profound sense of responsibility over both deaths.