Warcraft III's single expansion, The Frozen Throne added new heroes, units and terrains, and greatly expanded upon the original's campaign gameplay. The story continues where Warcraft III left off and tells of the Lich King's battle to free himself from the Burning Legion's grasp.
A bonus campaign involving the Orcs is included and can be accessed at any time, involving experimental RPG-like gameplay where the player controls a single hero rather than a complete troop, and completes quests for various quest givers while progressing in the story.
Since World of Warcraft was in development at the same time as The Frozen Throne, this game mode could be seen as a preview of what was to come.
