In Mass Effect 3, an ancient alien race known only as “Reapers”, has launched an all-out invasion of the galaxy, leaving nothing but a trail of destruction in their wake. Earth has been taken, the galaxy is on the verge of total annihilation, and you are the only one who can stop them. The price of failure is extinction. You, as Commander Shepard, must lead the counter assault to take it back. Only you can determine how events will play out, which planets you will save from annihilation and which alliances you will form or abandon as you rally the forces of the galaxy to eliminate the Reaper threat once and for all.

Mass Effect 3: Retaliation ups the challengeby adding treacherous environmental hazards to existing maps and will introduce the infamous Collectors as a new enemy faction in multiplayer.

Also making its way into the Mass Effect 3: Retaliation pack is a brand-new challenge system that will reward players for their accomplishments in multiplayer. This new feature will give players the ability to track and compare progress across different multiplayer challenges.

Mass Effect 3: Retaliation will be available for download on October 9 on Xbox Live and the Origin client software and on PlayStation Network in North America on October 9 and in Europe on October 10. In order to properly install the Mass Effect 3: Retaliation pack, users must also download and install the latest patch.

The entire pack will include:

• New “Hazard” Versions of Existing Maps – Wage war across six maps as a regular rotation of Firebases will be introduced to different hazards and traps. Survive the onslaught of Acid, Lightening, Meltdowns, Sandstorms, Swarms and Whiteouts!
• New Deadly Enemy Faction – Prepare to face off against the Collector Praetorian, Scion, Abomination, Trooper, and Captain. Reports have also come in that Cerberus has enlisted the Dragoon to their ranks and the Geth are deploying new Drones to the battlefield.
• New Unlockable Weapons – The Collectors have also brought deadly new weapons to the fight: the Collector Assault Rifle, Sub-Machine Gun, and Sniper Rifle.  Unlock these weapons and new equipment upgrades to build to your arsenal.
• New Class Kits to Unlock – A host of new characters have joined the war to fight this new threat, including the Turian Havoc Soldier and Turian Ghost Infiltrator. Additional class kits will be added as the weeks progress. 
• New Powerful Upgrades – Outfit your weapons with three new ammo modifications and fortify your gear with five unique upgrades to defeat even the toughest foes.
• New Multiplayer Challenge Feature – Think you are the best soldier in the Alliance? Make sure to track your progress in the new “Challenges” database. Complete various multiplayer assignments and feats of strength to unlock titles and banners to display in-game, and then compare your progress against your friends.

As part of the Mass Effect 3 Galaxy at War system, success in the cooperative multiplayer experience in Mass Effect 3 links back to the player’s single-player campaign. Gaining control over each theater of war will increase the player’s Galactic Readiness Rating, and in turn, can influence the player’s overall experience. Participation in the Mass Effect 3 Galaxy at War feature is optional.