Sallos is listed as spirit number 19 of the seventy-two in the Ars Goetia, the first book of the Lesser Key of Solomon (Lemegeton). The grimoire gives it the rank of Duke and places 30 legions of spirits under its command. The ranks used throughout the catalogue, king, prince, duke, marquis, president, earl (count) and knight, are borrowed from the hierarchy of a European royal court and the medieval nobility rather than from any infernal order of precedence, and the legion-counts serve as a conventional literary measure of a spirit's standing.
The particular office ascribed to Sallos, the powers it is said to grant an operator who "calls" it, is recorded in the entry's description. The material is set out here as a documented feature of an early-modern magical text, with no suggestion that the spirit is real or that the operations described have any effect; the Lesser Key is treated as a subject of historical and literary study, and no invocation or ritual instruction is given.