The content in the Legends of Urak expansion (included in the "Special Edition" of the game) revolves around various fables and stories. Earth, Fire, and Death each have a unique quest while Order has two quests.
The Earth quest is based on the epic poem Beowulf but involves many original battles and adventures Beowulf partakes in. The Fire quest revolves around a fire sorceress named Crispin who seeks out and slays a colossal ice drake in order to return the flow of lava to the fire capital. The Death adventure focuses on the necromancer's ability to raise the dead and employ them in battle. The adventure ends either by defeating a lich in battle and retrieving his staff for the death lord, or by keeping the staff, taking control of the death capitol and defeating the eldren queen. The first Order adventure is loosely based on the legends of Merlin and King Arthur and ends with the retrieval of the Holy Grail and death of Mordred. The second Order adventure is only activated by clicking in the center of the circle of life in the quests menu and has a unique lord named Sigfried who transforms as the game progresses. He saves the valkyrie Brunhilde and defeats Attila the Hun.
Source: Wikipedia, "Lords of Magic: Legends of Urak", available under the CC-BY-SA License.