Update: Looks like Leviathan has been dated. Xbox 360, PS3, and PC Mass Effect 3 players will be able to buy the new DLC on August 28. For PS3 users in Europe, the single-player add-on arrives a tad later, on August 29.
Yesterday, EA confirmed that Mass Effect 3 would be getting some single-player DLC, dubbed Leviathan, and we're getting solid information finally on the Reaper-centric content. No more speculation.
Comparable to Mass Effect 2's Lair of the Shadow Broker in size, Leviathan will be accessible pretty early in Mass Effect 3. The story revolves around the search for a weapon or thing that can supposedly kill Reapers. A Citadel scientist named "Bryson" was researching this mystery weapon when he wound up dead, murdered by a lab assistant who showed signs of indoctrination -- only BioWare is hinting as something deeper than that. From there, Shepard picks up the trail.
Turns out, the events of Leviathan can have an effect on the game's ending. No, it won't change it entirely, but there will be a few extras in the Extended Cut. Unlike the Extended Cut DLC, however, Leviathan is going to cost you an extra $10.
The add-on will have its share of new locales, including some kind of underwater environment, and BioWare has made the combat a bit more challenging by designing trougher maps to navigate and difficult objectives. One situation has Shep running back and forth carrying power cells and charging a generator while the power percentage is ticking down.
At least they're not skimping on content, but would you want to pay for more story DLC at this point, even knowing that you can't alter Shepard's fate?
Thanks for the tip, nnnddd101010!