Originally released on 2006-2-21, Galactic Civilizations II (GalCiv II) is a 4X Grand strategy game set in the 23rd century, when multiple alien civilizations scramble to conquer the galaxy, planet by planet, by force, diplomacy, influence (culture), or technology. GalCiv II focuses on the single player experience that consists of a Campaign mode and a "Sandbox" mode, and omits multi-player. The game is notable for its artificial intelligence, which is challenging without being given resources and abilities not available to the player, as is common in the majority of strategy games.

Galactic Civilizations II: Dark Avatar is the first expansion pack to the turn-based strategy game Galactic Civilizations II: Dread Lords. It added new features such as: Two new civilizations: a genocidal Drengin offshoot called the Korath and a civilization called the Krynn, A new campaign in which the player leads the Drengin Empire, The ability to create custom opponents, An "environment" statistic to planets, which will determine which civilization can innately colonize or what technologies will be necessary for other civilizations to colonize different planets, An enhanced role for espionage, special "Agents" being hired that can conduct various missions, such as sabotage or destabilization, on rival worlds, or act as counter-agents against rival agents attempting to conduct missions on the player's worlds, Asteroid fields to the space map, for players to mine for resources. Resources from asteroid fields are directed to planets where they increase manufacturing capacity, A great deal of new ship hulls and jewellery and The extermination of two civilizations during the campaign - the two exterminated civilizations will still be available in "sandbox" mode, but will not appear in the future releases of the game.

Galactic Civilizations II: Twilight of the Arnor is the second expansion pack to the turn-based strategy video game Galactic Civilizations II: Dread Lords. It added new features such as: The ability to destroy solar systems with massive ships called "Terror Stars", Unique technology trees, planetary improvements, and weapons for each civilization, A map pointer and custom scenario editor, New graphics that reduce graphic memory requirements by over 90% and a new map size that allows for games that may take millennia to complete

The officially supported Community Update, included in all recent releases of Ultimate Edition, fixes severe bugs in the AI that were present in Twilight of the Arnor.