The Curator of Harmonia is the sovereign of the Curacies of Harmonia and the Master of the Harmonic College of Archmagi. Early in the history of Harmonia, the Curator held more enumerated reserve powers; many were relinquished formally to the President of Harmonia or fell into disuse and are of unclear viability by the time of PRPG3.
Princess Nova, First Curatrix of Harmonia, Guardian of All Lawful Magic, is the incumbent Curator of Harmonia. (Specifically, Elite "Libby" Librarian is Curatrix; Exceptional "Elly" Librarian, her deceased 'twin sister', was not.) The position is for life. In the event of the Curator's death or resignation, the Harmonic College of Archmagi would theoretically elect a new Curator.