[From the manual]:
Warlords™ III: Darklords Rising™ (Darklords) is the much anticipated sequel to Warlords™ III: Reign of Heroes™. After much feedback from thousands of fans of the original, it became clear that much more than an add-on pack was needed to fulfil the desires of Warlords fans. A year later, the result is Darklords Rising. There have been substantial enhancements to the computer AI, multiplayer gameplay and game options (check out the "Choose Capital" option!), not to mention the addition of scenario and campaign editors. Darklords Rising also includes a healthy dose of new campaigns, scenarios, units, spells and of course heroes.
Warlords III: Darklords Rising is an eight-player game of conquest and diplomacy within the fabled world of Etheria. This mythical land is the stage for your ambitions. In the quest for final victory you will assemble vast armies, conquer and plunder mighty cities, undertake perilous quests, make and break alliances, and wield magical artifacts [sic] of great power.