From the back of box:

Long forgotten as myths of a time past, the Fallen have returned, bringing war to all the kingdoms of Hyrathia. It has been over a thousand years since the Convocaton of Wizards has had a need for a war mage, and now they must choose a Grand Siege Magus to take on that role, leading the wizards of Hyrathia against this ancient enemy. Only those with the highest skills in Spells, Incantations, and knowledge of the rare Magical Components can hope to wield the power granted a war mage.

In the game Wizard's Gambit you compete for the honor of leading the Wizards of Hyrathia to battle. An ancient rite, known as the Gambit, pits wizard against wizard in a competition where the victor gains the title and power needed to lead the Convocation to triumph over the Fallen.