Earlier this year, Tom Sykes managed to scribble down a description of Mark of the Ninja's Special Edition DLC before it disappeared into the shadows. Since then, we've been searching for more information on the elusive update - poking around in bins, and shining lights down rat-ridden alleyways. It turns out that all we needed to do was follow developer Klei's twitter feed, as they've now announced August 16th as the date of the DLC's release.
Mark of the Ninja: Special Edition DLC is arriving on Steam / XBLA on Aug 16! New costume, level, and TONS of developer commentary! August 6, 2013
As they mention, the DLC will add a new level, two additional items, and developer commentary to the game. More significantly, new styles of play will increase the number of non-lethal options available to players, for those who like their stealth to not be at the expense of a trail of blood and bodies.
The Special Edition DLC will cost $4.99, and other, yet to be announced, local equivalents.