A long time ago in a galaxy far away there was a game company called Williams. Now Williams wasn't like other game companies, no they were different, they didn't suck, they made the best arcade games and the best pinball machines around, and their small library of titles was extremely popular.
Along came 1984, in 1984 it was very popular for arcade game manufacturers to produce conversion kits to change old games into new games. So Williams decided to do the same thing. Now no one knows if this decision is what caused Williams to start sucking, or if they just coincidently started sucking all on their own, but either way this is the point that Williams starting sliding into a world of suckiness that eventually ended with them stopping production of all arcade games and all pinball machines in order to concentrate on slot machines.
Now where were we? Ah yes, 1984.
Williams released Mystic Marathon in 1984 as a conversion kit. 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. Around this same time Atari was also producing a game (Cloak and Dagger) designed to refit Williams cabinets, but that is neither here nor there.
The object of Mystic Marathon is to guide an elvin looking goblin in some sort of overland race. The game is incredibly frustrating and is just as hard as Defender, but without any of the fun factor.
In most arcade games of the day 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.
Apparently there are actually a few people who really like this game, but those people are in the minority, as this game was a huge flop, and few units were produced.
Today most of these machines (including one or two sample dedicated cabinets which never went into production) are almost exclusively in the hands of completist Williams collectors, as no one else wants to hold onto a $900 game that isn't any fun.
You can try it out for yourself in the Mame emulator. Sure, there is the outside chance that WMS Gaming might sue you for pirating it, but hopefully they are smart enough not to waste any more money on this title.