Sourcery

Sourcery is a fantasy novel by Terry Pratchett, published in 1988 and the fifth book of his Discworld series. The comedy of the Disc rests on a piece of invented physics: eight is a potent number there, wizards are the eighth sons of eighth sons, and the wizards who were themselves sources of magic once caused the mage wars that left parts of the Disc uninhabitable.

In this volume a sourcerer is born, the son of a wizard who was himself an eighth son, and the child arrives with the power of the old magic and a hat that instructs him. Rincewind, who had last been seen falling off the edge of the world, is returned to the story as the man who has to keep the boy from becoming the instrument of the wizards of the Unseen University.

By this point Pratchett was using the series to satirise fantasy's own conventions, and Sourcery takes the figure of the all-powerful wizard and looks at the institutions that would like to own a child of that kind. It is one of the earlier Discworld novels, which move quickly and end with the world's order slightly rearranged.