The new community campaign dubbed 'Cold Stream' is being made by Matthew Lourdelet, maker of '2 Evil Eyes,' which was Valve's first L4D2 featured campaign.

Valve is also soliciting opinions and suggestions from players. The work-in-progress campaign will be available for all to play "in the next few weeks," and a forum has been set up for feedback and suggestions. Valve explains that following the story-heavy DLCs The Passing and The Sacrifice, this new pack will add no new story or audio, so if you have an idea which calls for neither, head on over to the forum and suggest away.

The yet-unnamed DLC will be released for PC, Mac and Xbox 360 "sometime after Portal 2," which launches on April 20. Valve says that it will be subject to "Valve Time," the process whereby projects take as long as they take rather than being rushed to deadlines, noting that this "is a good thing, not a bad thing."