As the title suggests, the game is based on Arthurian legend. Both fictional and historical sources are used to recreate the atmosphere of the age of King Arthur and the Knights of the Round Table, and to draw out characters' names, history and relationships. The game's sources include medieval works such as Thomas Malory's Le Morte d'Arthur, modern ones such as Marion Zimmer Bradley's The Mists of Avalon, and a number of historical treatises on Arthur of the late 1980s. Spirit of Excalibur is a role-playing game in which the player is in control of a host of characters, rather than a single one, and as such he has to explore with them Arthurian England in an attempt to solve quests within the game and reach the final goal of uniting Britain under a single king.
The geographical setting for Spirit of Excalibur is a depiction of actual southern England with its cities, castles, villages, churches and other locations scattered throughout the land. The player starts by controlling a single character, Lord Constantine, but as the game proceeds he will be able to control many other knights and the armies they lead, not to mention Arthur's best friend and magician Merlin. All action takes place at two different levels: a so-called "map level" and a "scene level".
The game was followed by a sequel, Vengeance of Excalibur, in 1991.