The object of Mystic Marathon is to guide an elvin looking goblin in some sort of overland race. In most arcade games if you made a mistake you would lose a life, but in Mystic Marathon making a mistake, any mistake, simply meant it was impossible to win the race. Bump into something, oops, can't win. Choose the wrong path, can't win. Press jump at the wrong time, can't win.
Williams released Mystic Marathon as a conversion kit only. This was a cabinet specific conversion kit, as it came with a new control panel and other components that were sized to fit Williams cabinets only. (arcade-history)