Game description from the publisher:
Cosmic Alliance, the third expansion set for the Fantasy Flight Games version of Cosmic Encounter, brings 20 alien races, both original and classic, exploding onto your tabletop. Players will now stand petrified by the hideous Gorgon, be baffled by the puzzle of the Schizoid, and feel obsolete before the bionics of the Cyborg.
Cosmic Alliance also makes the Cosmos even bigger, adding another player (white) as well as rules for large eight-player games (if you own all three expansions). Finally, Cosmic Alliance introduces a new variant – team rules, which allow steadfast allies to dominate the Cosmos together!
This optional Team Cosmic variant places players in randomly determined teams of two, in which they'll attempt to conquer the Cosmos cooperatively. Without discussing their race selection in advance, partners sit opposite each other at the table, where they can occasionally offer a helping hand; whenever a player gains a new foreign colony, he can choose to instead give that colony to his partner.