Originally produced by Eon in the seventies, Cosmic Encounter has since been produced by West End Games, Mayfair Games, Avalon Hill Games, Inc., and Fantasy Flight Games. Each version is slightly different, but all share a core set of features.
Players represent alien races that are seeking to spread themselves onto five foreign worlds. To accomplish this, they make challenges against other players and enlist the aid of interested parties. But alien powers, which are unique to each race, give players ways to bend or outright break some rule in the game.