In Ars Theurgia Goetia, English alchemist and sorceror Gary St Michael Nottingham presents a precise and practical guide to working with the versatile spirits and wandering princes of the Theurgia Goetia, part of the seventeenth century Lemegeton, one of the most influential and significant of all grimoires. The full seals of the spirits are given for the first time, plus material from the Steganographia of the Renaissance mage Abbot Trithemius, an earlier work which heavily influenced the formation of this grimoire. Unlike many grimoires, the Theurgia Goetia heavily stresses the direction and conjuration time at which each spirit must be summoned. This is explained using the complex image known as the Compass Rose, which shows the hierarchy of the spirits and the thirty-two directions of their mansions. This work thus offers practitioners unique access in both time and space to the spirits and wandering princes of the Theurgia Goetia. The author includes detailed instructions on the magical tools needed for working with the spirits, including consecrations, the construction of the magic circle and triangle, and the preparation of the altar. The full ritual sequence of preparation, conjurations and license to depart is lucidly demonstrated, making this work suitable for both the beginner and the experienced practitioner. Ars Theurgia Goetia is Vol IV in Foundations of Practical Sorcery by Gary St Michael Nottingham.