The Ars Goetia is the first book of The Lesser Key of Solomon (the Lemegeton, 17th c.): the catalogue of 72 demons or spirits, each with its rank, its legions, its office and its seal. This page answers the basics and links to everything.
It is the first of the five parts of the Lemegeton. It catalogues 72 spirits —kings, dukes, princes, marquises, earls, knights and presidents— with each one's seal (sigil) and the "office" tradition assigns to it. The word goetia comes from the Greek γοητεία, "sorcery". Our base source is the edition by S. L. MacGregor Mathers and Aleister Crowley (1904), which gathers earlier manuscripts such as Sloane MS 2731.
The Lemegeton or Clavicula Salomonis Regis ("The Lesser Key of Solomon") is an English grimoire compiled in the mid-17th century in five books: Ars Goetia (the 72 demons), Ars Theurgia-Goetia (spirits of the air), Ars Paulina (angels of the hours), Ars Almadel (angels of the four altitudes) and Ars Notoria (orations for memory). You'll find them all as facsimiles, translated, in the Library.
If you are looking for a particular entity, use the catalogue of the 72 spirits: each entry separates name variants, rank, office, seal, provenance and what the source says about invocation. If you are looking for a term such as Goetia, Lemegeton, sigil or enn, the glossary gives definitions in context. To check the text, see the source page and the manuscript library page; to compare names and offices across witnesses, see the collation of the Livre des Esperitz and Liber Officiorum Spirituum. The site always distinguishes an old source from a modern addition.
According to the sources, the operator draws the circle and the Triangle of Art, lights the candles, engraves the spirit's seal and recites the conjuration; if the spirit tarries, the operation orders you to constrain it again, and at the end you give it the licence to depart. All of this —documented, and kept separate from what modern practice added— you can walk through step by step in The Practitioner's Table, our historical-educational simulator. It is historical material, not a guide to actually summon.
Each demon has its page with seal, rank, legions, office, provenance and how it is summoned: start with Bael, Paimon, Asmodeus or Belial, search by name or power in the catalogue of the 72, and download the seals from the gallery (CC0).
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