Mayfair, 1991, 3-6 players, ages 12 and up. This game has been around in various editions since the early 1970s, but I've been told that the Mayfair version is the best. The first non-prototype version was released by a company named Eon circa 1977 (followed by 9 expansions up through 1983). After that there were the West End Games and Games Workshop versions in 1986, and most recently the Hasbro/Avalon Hill version (which added a lot of unwiedly plastic pieces to the pot and not much else). Mayfair released its own expansion set "More Cosmic Encounter" in 1992, along with a simplified version called "Simply Cosmic" is 1995.
The game itself is fairly simple. Each player starts out with 20 counters on their home planetary system (divided up amongst 5 planets). The goal of the game is to move some of your counters to planets in the other players' systems and establish 5 new bases outside of your home system. This is accomplished through a system of "challenges". First, you flip over a destiny card which establishes the color of the system in which you can issue your challenge. Then you pull up to 4 counters from your existing pool and place them on the "Hyperspace Cone". The person you are challenging in turn also places their counters (from the planet in question) onto the cone. Next, alliances may be invited - either to help the attacker or the defender. Allies place up to 4 of their own counters on the appropriate end of the cone. Then each player plays a challenge card. This can be an attack card or a compromise card. If both players play attack cards, the attack number (1-40) from each card is added to the number of counters for the specified side. The side with the highest total wins. If the attacker wins, all of his and his allies counters get placed on the planet (giving them all a new base) and all of the defending player's and allies' tokens get placed into "the warp" (a place for dead tokens to go until such time as they get pulled back into play). On the other hand, if the defending player has the higher total, all of the attacking player's and allies' tokens go to the warp. Players who allied in a successful defense are rewarded with a card from the Challenge deck for each counter they committed to help in the defense of the planet. The other kind of challenge card one can play is the "Compromise" card. If one player elects to compromise and one does not (plays an attack card), the player playing the compromise card loses the challenge but is awarded a card from the attacker's hand for each token he lost in the attack. If both players play compromise cards they have one minute to arrive at a deal (with all of the other players supposedly counting down "one-thousand one, one-thousand two, etc" in a effort to be as irritating as possible). In addition to the challenge cards, players can also draw "Flare" and "Edict" cards, which can aid them in a challenge. Finally, each player has an innate "special ability", unique to the Alien Power card they draw at the beginning of the game. It is the latter feature that adds the most variety to the game and gives it its supposed "uniqueness".
This game has a somewhat legendary position in gaming history mainly because (and I hope this is not apocryphal) the people who helped design it went on to create (or at least inspire the creation of) Magic: The Gathering. It is supposedly the original game that adopted the strategy of a base game that then breaks its own rules with individual cards. Having said that, I'm still not all that impressed with the game (although there are certainly legions of fans who would disagree with me). The game itself is very abstract. I mean, it's pretty much a Science Fiction game in name only. The "planets", "counters" and "bases" could be pretty much anything. You might as well be playing Backgammon. Secondly, this whole business of having hundreds of different Alien Power cards that "break the rules of the game" (the honest to gosh marketing spiel on the box) makes for a hell of a lot of rules controversy. When we played we spent way too much time hammering out rules rulings. Finally, the game really lacks a feeling of how well one is doing. Bases are formed and lost, counters move around from one planet to the next and into and out of the warp, and one turn to the next you're really don't know how things are going for any one player. Frankly, this whole random mutability thing feels a lot like playing "Candyland" to me. One minute it feels like the damned thing could go on for years, the next minute somebody has won.
"More Cosmic" (I own it, I've looked at it, I doubt I'll ever make any use of it), basically adds all of the Eon expansions in one swell foop - dozens of new alien powers, the ability to play with up to 9 players (yikes), more Flares, Edict, and Challenge cards, "Moons" (don't ask me), "Kicker" cards (ditto) and "Lucre" (re-ditto). "Simply" basically takes the base game and pares it down by eliminating all but about 9 alien powers.
So anyway, it's an important game, it's a classic game, and it's a game loved by millions - just not by me and the people I game with.