Duke

Duke is the single most common rank in the Goetia's catalogue of seventy-two spirits, assigned to a larger share of the list than any other title, King, Prince, Marquis, Earl, President or Knight included. The rank name itself descends from the Latin dux, meaning leader or commander, originally a Roman and then late antique military title for a regional or frontier commander before it hardened, across medieval Europe, into a hereditary aristocratic rank just below a prince, and it is this later feudal sense, a great nobleman commanding forces and territory but still subordinate to a king or prince, that the grimoire tradition borrowed wholesale for its own catalogue of spirits.

Because Dukes are so numerous in the list, the rank functions less as a mark of any single spirit's particular importance than as the default or baseline title for a demon of substantial but not supreme standing, commanding anywhere from a modest number of legions up to several dozen depending on the individual entry, a considerably wider range of stated military strength than the more tightly defined Kings or the lower Knights show among themselves. Well known Dukes in the catalogue include Agares, said to teach languages and cause earthquakes, and Vepar, credited with governing the waters and guiding ships, both illustrating how varied a single rank's stated powers could be despite sharing one feudal title.

Sources Lemegeton Clavicula Salomonis (The Lesser Key of Solomon)Anonymous (unidentified compiler) with Encyclopaedia Britannica (online academic reference)Encyclopaedia Britannica editors

Duke is the largest rank in the catalogue by a wide margin. Twenty three of the seventy-two spirits hold it, close to a third of the book, and between them they command 752 legions, which is more than the nine kings command together.

A category that absorbs a third of a taxonomy is usually the default rather than a description, and Duke reads that way here. The kings are marked out by precedence, the presidents by a civil and teaching function, the marquises by their place between the two, and the single knight by being an outlier. Duke is what a spirit is called when the compiler had nothing more specific to say about its standing, and the range of offices filed under it is correspondingly wide.

The legion counts support the reading. They run from 10 at the lowest to 60 at the highest, the broadest spread of any rank apart from King, and the average of roughly 33 sits close to the middle of the whole catalogue. There is no characteristic Duke.

The twenty three include Agares, second in the book, and run through Barbatos, Gusion, Eligos, Zepar, Bathin, Sallos, Aim, Bune, Berith, Astaroth, Focalor, Vepar, Uvall, Crocell, Alloces, Murmur, Gremory, Vapula, Haures, Amdusias and Dantalion, ending with a spirit credited with knowing the thoughts of all people.

Murmur is given in the Ars Goetia as a Duke and an Earl together. This collection files each spirit under a single rank, so compound titles are represented by the first of the pair.