A sourcerer is born - a wizard so powerful that by comparison all other magic is just mucking around in pointy hats. And his very existence brings the Discworld, which is of course flat and rides through space on the back of an enormous turtle, to the very verge of all-out thaumaturgical war*. All that stands in the way is Rincewind, the failed magician, who wants to save the world, or at least...