At its Summer Showcase, Electronic Arts announced the first story-driven single player DLC for Mass Effect 3. As expected, it is called Leviathan. According to earlier reports, the DLC involves Shepard rescuing a scientist from an indoctrinated mining facility. It was taken over by a Reaper defector named Leviathan, who left his collective when he killed one of his own kind.

Electronic Arts' official description 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. Explore uncharted systems and new areas on the Citadel, interact with brand new characters, unlock the AT-12 Raider shotgun and M-55 Argus Assault Rifle and discover more about the mysterious history of the Reapers.

The DLC is scheduled to release this summer. It will be available for $10, or 800 Microsoft Points.

Update: Also available on August 7 is the new single player Firefight Pack, which features "two powerful new weapons and five bonus weapons" available for $2, or 160 Microsoft space bucks.