Galactic Civilizations II: Twilight of the Arnor includes a massive payload of new content and features requested by the series’ devout fanbase. In addition to a new campaign that ties up the Dread Lords saga, Twilight of the Arnor adds civilization-specific technology trees and planetary improvements that add even more flavor to each alien race, while greatly expanding the strategic depth of the game. A vast array of new ships, weapons, starbases and ship components will be available to players, including the devastating Terror Star, which can annihilate entire star systems. Galactic Civilizations II: Twilight of the Arnor requires GC2: Gold Edition or GC2: Dark Avatar.

The initial Twilight of the Arnor beta test includes the following features, while others will be added in upcoming beta releases:

- Three new technology trees to add unique flair to each galactic civilization
- Updated AI that makes computer-controlled factions act even more like human opponents
- Several new planetary improvements to give players more options when developing conquered planets
- Lots of new unique starship components that allow players to create their ultimate personalized battle fleets
- Improvements to fleet battles (how can we spin this one?)
- Updated graphics that help to further immerse players in the game