Galactic Civilizations III - Retribution draws the story arc begun in the base game and carried through subsequent DLC to a close. In addition to a campaign, this DLC adds two popular races from Galactic Civilizations II, the Drath and the Korath, both of which feature in the campaign.
This expansion adds a few new features, including artefacts, hypergates, a reconfigured technology tree, and a few other minor improvements. Artefacts can be found on planets and provide a bonus to adjacent hexes, but also when developed can provide a variety of single-use boons to the player who controls them. These boons include things like a temporary happiness boost, a free ship, a permanent increase to a fleet's power, and a host of other options. Hypergates can be constructed to speed up movement around the galaxy along fixed paths, speeding up gameplay on larger maps.