Mass Effect 3: Retaliation, a multiplayer expansion pack, will be released next week for free.

Noted as the biggest expansion to date by BioWare, in Retaliation, The Collectors have returned as a new enemy in multiplayer matches.

Players will face off against the Collector Praetorian, Scion, Abomination, Trooper, and Captain. Cerberus has enlisted the Dragoon to their ranks and the Geth are deploying new Drones to the battlefield.

A host of new characters such as the Turian Havoc Soldier, Turian Ghost Infiltrator, more are being added on a regular basis across six maps, featuring new environmental hazards and traps.

A regular rotation of Firebases will be introduced to different hazards as they come under attack. Players will have to “survive the onslaught” of Acid, Lightening, Meltdowns, Sandstorms, Swarms and Whiteouts, as well as deadly new weapons: the Collector Assault Rifle, Sub-Machine Gun, and Sniper Rifle.

These weapons and new equipment can be unlocked.

A new “Challenges” database in Retaliation will also be available, where players can keep track of completed multiplayer assignments and “feats of strength”, which will unlock titles and banners to display in-game.

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Mass Effect 3: Retaliation launches October 9.