The Mass Effect 3 Retaliation pack is set to be the biggest update to the multiplayer mode yet. The chitinous villains of Mass Effect 2, The Collectors, will return. Praetorian, Scion, Abomination, Trooper, and Captain variants will form a new 11 wave assault. Kill them, get cash, buy boxes and open them to dramatic inception "BWAAAARM" noises. If you're lucky, you might unlock a new class like the Turian Havoc Soldier, or the Turian Ghost Infiltrator, or a new collector-themed weapon.
Six of Mass Effect 3's multiplayer maps will suffer environmental hazards and traps. It's not clear how these will affect the maps precisely, but the announcement post on the Mass Effect 3 site mentions "Acid, Lightning, Meltdowns, Sandstorms, Swarms and Whiteouts."
Retaliation will also add more powerful ammo mods and introduce a challenge system that'll reward milestones (a certain number of kills with a certain gun, for example) with points that can be spent on banners that you can flaunt in the player lobby.
Retaliation will be released for free next Tuesday, October 9. Here's a rousing trailer set to music that's really far too exciting for this time of the morning.