A spell for Chameleon / Anthony, Piers

Exiled from the land of Xanth, twenty-five-year-old Bink must prove to his people that he holds magical powers.

At age 25 Bink was exiled from the magic land of Xanth because he had no magic spell that was observable to his people. But both the good genie and the magic wall chart insisted that he did. How could he prove he had magic?.