Tallus Penitax was the Professor of Darkness during the Rook trilogy. He, along with the Professor of Light, Ulbus Vespius, deserted the evil Guardians of Night and formed an allegiance with the Librarians. He was a member of the Council of Three, and later, the Freeglades Council. Tallus Penitax was the one who put forth Rook's name for consideration as a Librarian Knight.