The first info and screenshots were initially revealed during last week's "Questions with Steve Episode 5" (included below).
Dead Space 2: Severed DLC extends the single-player story with the addition of two standalone chapters featuring Dead Space: Extraction's Gabe Weller and Lexine Murdock.
The story of Weller and Lexine runs parallel to Isaac's adventure in Dead Space 2, but the players will take on the role of Gabe Weller, a Sprawl security guard that fans may remember from Dead Space: Extraction, and has to fight the Necromorph to get Lexine and himself to safety.
The new DLC is set to be released soon.