Sid Meier's Alien Crossfire
Sid Meier's Alien Crossfire, published in September 1999, is an expansion pack for Sid Meier's Alpha Centauri. It was designed by Timothy Train and other members of Firaxis Games. Alien Crossfire features seven new factions (two of which are non-human) and multiple new technologies.
The main storyline element added to the game is the "alien crossfire" itself. The two alien Progenitor factions are locked in a civil war: one side, the Usurpers, wishes to exploit Manifold Six (the Progenitor name for Planet) for military purposes; the other side, the Caretakers, wishes to prevent this and leave the planet alone. Both factions sent ships to Manifold Six to settle the matter once and for all. Unfortunately for them (but probably fortunately for the human factions on Planet), the battle went badly for both sides and they ended up crash-landing on Planet. Lost in the crash are countless alien lives and virtually all of the alien research and technology. Their civil war continues, however, and both factions dream of the day that they can send for reinforcements and crush the other faction.
Progenitor factions have the ability to always target research (human factions, by default, can only choose general research paths.) In addition, the Progenitors have a unique victory condition - by researching up the tech tree, they can eventually build a Resonance Communicator, allowing them to summon the bulk of their forces to Chiron, overwhelming all other factions.
Initially, Progenitors and humans cannot confer with each other - they must research the appropriate technology (Progenitor Psych for human factions, Social Psych for Progenitor factions) to understand how to communicate between the species. Also, Progenitor and human living requirements are radically different - when one species takes over a city of the other species, those residents that survive the conquest are forced out in Colony Pods. Since the two sides belong to different species, they are also able to commit atrocities, such as destroying bases and using nerve gas, against each other without fear of political repercussions. The only exception to this is the use of planet-busters since it affects Planet negatively.
The Progenitor factions can win with Progenitor Victory condition. The player must construct the Resonance Communicator. The Resonance Communicator is a combination of six Subspace Generators. In order for a Subspace Generator to be activated it must be at a base size ten or larger. The Resonance Communicator is used to call the Progenitors' home fleet, which is much more powerful than all the human and the other Progenitor factions combined, so the player wins the game. Even if Cooperative victory is enabled, only the faction that built the Resonance Communicator is considered to have won.
