Custom Civilization Opponents. Players can now design their own opponents within the game and then play against them. This includes both what the opponent looks like but also how it plays.

Espionage Agents.  Many of the reviews of Galactic Civilizations II have made mention of how the game allows players to win through many different strategic paths.  Espionage agents give players the ability to win through covert operations. Spend money on espionage to hire agents who can sabotage production, research, morale, farming, etc. on enemy worlds. Or use them to snuff out enemy agents on your worlds.

Special Worlds.  In Galactic Civilizations II, all worlds could be colonized by all players.  That will change. In Dark Avatar, each world will be of a certain environment and only civilizations that know how to build colonies on the proper environment can colonize until they research the proper technology.

Asteroid Fields.  Near worlds are asteroid fields which can be exploited by nearby worlds by players. Players will have a variety of asteroid bases they can construct. No longer are planets and galactic resources the only types of "space terrain".

Diplomatic Treaties. Players will be able to establish research and economic treaties with alien civilizations. In this way, they have other sources of money and research and have more tools to influence diplomatic relations.

New Computer AI options.  The advanced artificial intelligence in Galactic Civilizations II has been one of the most appreciated features of the game.   For the expansion pack, players will be given new options on just how the computer player will play (what algorithms it will make use of, whether it will "cheat" or not, how much CPU to give it) in order for players to get the best experience possible.

Two new races. Two new civilizations will be joining the mix.

New Ship parts. The popular ship design feature will get a lot of new content to design all kinds of new ships.

The new campaign.  A new mini-campaign will also be included to continue the story where things left off at the end of Galactic Civilizations II: Dread Lords.

MEGA Events. Users can optionally enable mega-events. These events can dramatically alter the course of the game. They're not completely random, intelligent algorithms analyze the galaxy and intentionally upset the balance of the galaxy -- civil wars, plagues, rising dread lords, new game rules, etc.

Super-Abilities. Each civilization now gains its own unique super-ability that is immensely powerful. The super-isolationist can keep ships from traveling more than a certain speed in their sphere of influence, the super-manipulator can more easily get civilizations to go to war with each other via diplomacy, the super-warrior gets extra ships, and so on.  Each civilization will feel more unique and have very powerful advantages.

New stream-lined technology tree. The Galactic Civilizations II technology tree gets a make-over to make it more stream-lined and interesting.

Visual Make-Over. Hundreds of little tweaks and touches to how the game looks to make it visually more interesting and more engrossing.

Templates. Players can design ships and save them as templates so that in the future, they can start off with a basic design.

User-assignable default AI ships. Players can not only design their opponents but assign what their ships will look like. Design your own set of sci-fi/fantasy ships and then assign those ships to be used by a civilization of your own design.