The Great Old One of Power (力の旧支配者, Chikara no Kyū Shihai-sha) is the mysterious entity within the Book of Eibon who's affiliation in Madness is "Power". Formerly one of the Eight Shinigami Legions, he was later captured at an unknown point by Noah though chooses to reside within the Book of Eibon as part of an self-imposed exile.