Galactic Civilizations II: Dark Avatar revisits Stardock's sci-fi universe, adding a multitude of new features and options to further enhance the strategic depth of the game. Featuring new single-player campaign that sees the elimination of two of the game's alien races and the introduction of several others, Galactic Civilizations II: Dark Avatar also allows players to create their own custom opponents, tweaking their behaviour, what they look like, what their ships look like and play style to develop truly unique enemies.

The expansion also introduces resource-rich asteroid belts, unique planets requiring advanced technology to colonize, spies to assist or prevent destabilization and sabotage, an Epic Generator that creates a unique story from each game played, advanced diplomatic treaties, new ship components, improved AI options and much more.