Mass Effect 3: Retaliation is a substantial DLC expansion focused entirely on the cooperative multiplayer mode, requiring the base game to play. This content significantly escalates the challenge by introducing the formidable Collector faction as a new enemy type and adding treacherous environmental hazards—like acid and lightning—to existing maps. It enhances the experience with a new Challenge System for tracking progress, unlocking titles, and comparing achievements, alongside new Turian class kits and powerful Collector-themed weapons to augment player arsenals.
The central addition to this downloadable content is the introduction of the infamous Collector faction as a new enemy type in multiplayer operations. Players will now face off against specialized Collector units, including the formidable Collector Praetorian, the Scion, the Abomination, the Trooper, and the Captain. Furthermore, existing enemy factions have received reinforcements, with Cerberus deploying the Dragoon and the Geth introducing new Drones to the battlefield.
To further complicate survival, existing multiplayer maps have been updated with treacherous environmental hazards. Players must now contend with dynamic dangers such as Acid pools, Lightning strikes, Meltdowns, Sandstorms, Swarms, and Whiteouts, forcing tactical adjustments to established combat routines across six different maps.
A major system overhaul comes in the form of a brand-new Challenge System. This feature allows players to track and compare their accomplishments across various multiplayer assignments and feats of strength. Successfully completing these objectives rewards players with unlockable in-game titles and banners, providing a persistent measure of progress that can be compared against friends.
The fight against these escalating threats is supported by the introduction of new playable character kits. Among the initial additions are the Turian Havoc Soldier and the Turian Ghost Infiltrator, with more class kits scheduled to be added following the initial release.
The enemy forces also bring new weaponry into the fray. Players can unlock and utilize new Collector-themed weapons, specifically the Collector Assault Rifle, Sub Machine Gun, and Sniper Rifle. Enhancing existing loadouts are three new ammo modifications and five unique equipment upgrades designed to help squads overcome the heightened difficulty.
As downloadable content, this package requires the base game, Mass Effect 3, to access and play. It integrates directly into the existing multiplayer structure, adding layers of content and mechanical variation rather than offering a separate campaign or standalone experience.