Bioware has announced that its upcoming Mass Effect 3 DLC, Leviathan, will be available on August 28. This is the first piece of post launch single player DLC for the game, and takes place midway through the adventure. Not many story details are known about Leviathan, but the official description from Bioware is as follows:
Something lurks in the dark corners of space, something powerful enough to kill a Reaper. Shepard must discover the most closely guarded secret in the galaxy before the Reapers silence it forever. Discover more about the origins of the Reapers as you race across the galaxy to find the Leviathan. Unravel the dark history of the Reaper Race before it is too late.
Taking place during the events of Mass Effect 3, players will be thrust into the darkest corners of space where they will hunt a mysterious being rumored to be powerful enough to destroy a Reaper. As they race against time, they will begin to unravel the secret of the Leviathan.
There are also choices that can be made that will further change the ending of the game, though to what extent is unknown, as the games ending was rather controversial when it was released, which prompted Bioware to release an exended ending for the game, so it will be very interesting to see how this affects how the end plays out.
Leviathan will be available On PS3, Xbox 360, and PC.