The Emperor or Empress of Avalon begins the game as King Leon and later plays as his various heirs down through the game years. Leon hands his kingdom over to his son, Gellard. At the end of Gellard's reign, the player is able to choose his or her own successor and pass on Gellard's abilities to them. At the end of each generation, he or she will be given a choice of four heirs. Their identity is based on a combination of chance and anyone whom the player has assisted or allied within in a past generation.

Long ago, a legendary band of warriors known as the Seven Heroes rose to save the world from a devastating monster invasion, only to vanish without a trace once the battle was won. A thousand years later, the Seven Heroes return, but they are no longer saviors. Twisted by dark powers, they descend upon the continent to sow ruin. Leon, ruler of the kingdom of Avalon, takes up the fight against them, and when he falls, the struggle passes to his son Gerard and the generations who follow. Through a mystical power called Inheritance, each ruler bequeaths their strength, skills, and unfinished war to the next, allowing the crown of Avalon to endure across centuries. As emperors and empresses rise and fall, they expand a fledgling realm into a mighty empire, leading their chosen champions across a shifting world in an ages-spanning campaign to hunt down the corrupted Seven Heroes.