The DLC adds a new Survival Mode, a faster-paced game mode that has players facing off against increasingly frequent waves of the undead across 12 specialized maps.

Valve's testers had yet to have a match last longer than nine minutes as of early March, and it seems that anything over 14 minutes will be ridiculously impossible, as the L4D Blog points out that Tanks will spawn every 14 seconds or sooner at that point.

"Given the extreme pace of Survival Mode, the number of zombies killed in a single round often outnumbers an entire campaign," wrote Valve's Kerry Davis and Scott Dalton, adding that one goal was to "have games that regularly last under ten minutes."

In addition, the pack brings Versus Mode support to the Dead Air and Death Toll campaigns, finally enabling Versus play for all of the game's four main campaigns.

While Valve had previously stated that the pack would arrive by April 21, the studio had yet to provide a more specific timeframe for the PC DLC, as an earlier announcement only pertained to the Xbox 360 release. However, word that PC gamers won't have to wait for the content comes as little surprise, given Valve's past support of the platform.