The newest single-player add-on for Mass Effect 3 comes out this week and it assembles characters from the previous ME games for an all-new adventure. Here's the official description:

When a sinister conspiracy targets Commander Shepard, you and your team must uncover the truth, through battles and intrigue that range from the glamour of the Citadel's Wards to the top-secret Council Archives. Uncover the truth and fight alongside your squad—as well as the cast from the original Mass Effect and Mass Effect 2, including Urdnot Wrex!