This game is the main attraction in the line that gave the world Ace of Aces. Each player has a character card, booklet, and special movement cards for one of about fifty (and growing) medieval-fantasy characters. Characters can range from barbarian warriors to animated skeletons to elven archers to unicorns - even two different dragons. Booklets are traded and, as each player selects a move, a reference grid in the books determine the results (wounds, off balance maneuvers, and so on). Combat continues until one fighter or the other expires.
The Lost Worlds system was licensed for use in Queen's Blade, and subsequently in Queen's Gate. All the games are completely compatible with one another.
An interesting feature of the Lost Worlds system is that it is designed to allow characters to advance as they succeed. In theory, you are supposed to keep track of your progress with each character, and if one is utterly killed, it will have to start over without its improved skills.