Twelve of the seventy-two are ranked President, commanding 446 legions, with counts running from 29 to 60. That is a narrow band and a high floor: no President in the catalogue commands fewer than 29 legions, which is more than the minimum for any other rank including King.
What holds the twelve together is a curriculum. Read their entries in sequence and the Presidents come out as the teaching rank of the book. Marbas is asked about mechanical arts and about diseases. Buer is credited with moral and natural philosophy, logic, and the virtues of herbs. Marax teaches astronomy and the liberal sciences and the properties of herbs and stones. Foras is given logic and ethics along with the virtues of herbs and stones. Ose and Amy are both credited with the liberal sciences, Amy with astrology in particular. Caim is asked about the voices of birds. Glasya-Labolas is credited with all arts and sciences at once.
Set beside the Kings, who are addressed with protocol, and the Dukes, who do a little of everything, the Presidents look less like a rank in a court than like a faculty in a university, and the offices attributed to them read as a syllabus of the medieval arts with natural magic added.
The twelve are Marbas, Buer, Botis, Marax, Glasya-Labolas, Foras, Malphas, Haagenti, Caim, Ose, Amy and Valac. Botis, Glasya-Labolas and Marax each carry the title jointly with Earl in the text, and are filed here under the rank given first.