Bioware has launched a new trailer to provide backstory for the free multiplayer add-on.
The add-on expands Mass Effect 3's multiplayer with six new human classes, new weapons and a new platinum difficulty setting.
It will also add three new maps based on London, Rio and Vancouver, as was leaked last month.
New character classes include N7 Fury, N7 Destroyer, N7 Demolisher, N7 Paladin, N7 Shadow and N7 Slayer.
Fury operatives are described as incredibly fast and unpredictable, Destroyers wear the T5-V Battlesuit, making them slow but powerful, while Demolishers can "create a supply pylon that stocks allies with an unending reserve of grenades and thermal reloads".
Paladins, meanwhile, carry powerful omni-shields into battle, Shadows are described as slippery combatants, while Slayers use dizzying sword attacks and are hard to pin down due to their ability to slip fire.
The 'Earth' DLC is available today (July 17) on PC, Xbox 360 and PlayStation 3 in North America. It will release for PlayStation 3 across Europe on July 18.
Screenshot gallery - images of Mass Effect 3 'Earth' DLC below: