The Master Edition is an updated release of the game Consortium. For some portals such as Steam it replaces the original version of the game released previously and adding portions as free DLC, while for others (GOG) it is the first version.
It updates the original game with improved core combat mechanics and artificial intelligence. The game performance has been improved to make it run faster on slower machines. There is updated controller support and a general polish to the choreography (character expressions, gestures) during various scenes. Characters now for instance use hand panels. There are balance changes to the Zenlil Combat mini-game, many bugs were fixed and for the Steam version there is leaderboard support for the Civilian Defense training scenario.
In addition it contains the free DLC Consortium: Soundtrack and Discoveries, which was also included by default with the original version of the game.