Marquis is one of the ranks assigned to the spirits catalogued in the grimoire tradition, and above all in the Ars Goetia, the first book of the seventeenth-century Lesser Key of Solomon (Lemegeton). It denotes a middle-ranking noble spirit, likewise credited with command over a number of legions.
The ranks of the spirits
The Goetia lists seventy-two spirits and gives most of them a rank, King, Prince, Duke, Marquis, Earl or Count, President, or Knight, borrowed from the feudal and civil offices of the human world, together with the number of legions each is said to command. The scheme draws on earlier sources, notably the Pseudomonarchia Daemonum printed by Johann Weyer in 1577.
The rank is described here as a feature of these documented magical texts, studied as historical literature; the spirits so ranked are not reified.
Marquis traces to Old French marchis, itself from marca, a border march or frontier territory; the parallel German Markgraf, "count of the march," shows the same underlying idea taken up independently in the Holy Roman Empire. Both titles denoted, in their original medieval use, a nobleman entrusted with defending a frontier zone rather than an interior province, a responsibility that in principle carried more independent military authority than an ordinary count's, even though the peerage eventually ranked Marquis just below Duke. The Goetia borrows the word purely for its aristocratic weight, with no trace of the frontier-defence sense that originally gave the title its point.
Sources Lemegeton Clavicula Salomonis (The Lesser Key of Solomon)Anonymous (unidentified compiler) with Encyclopaedia Britannica (online academic reference)Encyclopaedia Britannica editors