This article examines a small treatise of magic that is included in the General estoria, the ambitious account of the history of the world commissioned by the Castilian king Alfonso the Learned. The General estoria ascribes this treatise to several authorities who have Arabic origins. I argue that it is not a translation of Arabic sources but rather an elaborate original tract. The treatise classifies magic into three categories, each represented by mythological female characters. This threefold division of magic was inspired by a similar classification in the Picatrix, which was translated in Alfonso's scriptorium and is considered the most significant medieval book of magic. The first two categories of magic, imágines and confaciones, were taken from the Picatrix and correspond to the Arabic ṭilasmāt and nīranjāt; however, the Alfonsine compilers changed the Picatrix's third category of magic from alchemy to casting lots and words and proverbs, which I associate with textual amulets. I suggest that this classification of magic and the changes from its source were influenced by a quest for consistency with the Siete Partidas as well as a desire to make the magic relevant to the needs and practices of a contemporary Castilian audience.