All magic is suddenly gone. No mage can sling sorcery anymore. This upsets all empires and civilizations. It is soon discovered though, trough the combined work of mystics, scholars and dreams, that all the magic has been drawn into a single orb in a vast tower located at one of the poles. Whoever gets there first wins the greatest price in history, access to all the magic in the world. But who owns the tower?
A basin type hole in the middle of the plains. Once every so many years the rains come very hard and flood this place. Maybe that is where the tribes congregate for their tribal meetings.