In Mass Effect 3: Omega, the notorious criminal haven has been taken over by Cerberus and Commander Shepard will have to join up with Omega's former leader, Aria T'Loak to take back the station. There's also a side-plot about helping a Turian mercenary free the slaves on Omega, but mostly it looks to feature new enemies (including a new Reaper) in four action-heavy missions.
The new DLC will also, in a way, be the first glimpse at the future of the Mass Effect series. That's because Omega was developed by Bioware Montreal, the developer that recently announced it is working on a brand new Mass Effect game. The new game will be "exploring new directions, both on the gameplay and story fronts." In the meantime, the new DLC will provide more of the classic Mass Effect gameplay fans of the series crave.