Mass Effect 3 will be receiving single-player DLC soon. Voice actor Anthony Skordi confirmed that a new adventure dubbed Leviathan is currently in development at BioWare.
Skordi, who shared this information with Eurogamer, is playing the titular character. Leviathan is a rogue Reaper who set out on his own after killing another one of its kind. This Reaper settled at a mining facility and took over its inhabitants' minds through Indoctrination.
In the DLC, Commander Shepard and his crew will head to the mining facility to rescue a scientist, Ann Brynson. Brynson will live or die depending on the players' actions. It's also possible to recruit Leviathan for the war effort against the Reapers.
Leviathan will be the first single-player DLC for ME3, other than the Extended Cut add-on that expanded the game's endings. The DLC's existence was revealed by >data uncovered in Extended Cut.
Although the Mass Effect trilogy is now over, the Reapers are still sort of mysterious. This content should give us a bit more insight into their "society." Perhaps we'll even find out more about their mysterious creators?
Now that everyone knows Leviathan exists, it's high time for BioWare to actually announce it.