S3 E4: A Sudden Wild Magic
The restraints of knowledge harmed this wild power. In order to use it, Zillah could not know what it was. It would only answer a being as untrammeled as itself.
Time for elves, centaurs, demons, gods, witches, monks, princes, soulbonds, spaceships, sex, death, and an ever-present toddler, in undoubtedly the wildest book of Diana Wynne Jones' career to date.