Our resident historian Marzhin wrote a detailed plot summary (with an introduction by rogue) for all eight chapters of Heroes Chronicles, the standalone Heroes III scenarios that were published by 3DO a couple of years ago. The long quest of Tarnum, the same character that was part of the Heroes of Might and Magic IV chaos campaign, begins in Warlords of the Wasteland:

"This story takes place before the foundation of the kingdom of Erathia. Once upon a time, the great barbarian King Jarg ruler over those lands. But then the Wizards of Bracaduun came and enslaved the barbarian people. Young Tarnum learns the long-lost history of his people from the last bards and decides to do anything to break the Wizards' rule. Becoming the new Barbarian King, he leads the clans against Bracaduun."